Domain registration fails

While testing the domain registration from the app (using domain credits), the last step failed for me without any snackbar or a message. There is just this whiteish circle that appears in the middle of the screen and that's it.

The error looks like an unexpected API object.

I'm setting the priority to low because it's only happening on one of my accounts and it doesn't happen to another person testing the same thing.

The error in the logcat is:

2020-12-09 16:12:41.493 4224-4224/org.wordpress.android.prealpha E/WordPress-API: Volley error on https://public-api.wordpress.com/rest/v1.1/me/shopping-cart/169844210/?locale=en_US
    com.android.volley.ParseError: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2247 path $.products[1].extra
        at org.wordpress.android.fluxc.network.rest.GsonRequest.parseNetworkResponse(GsonRequest.java:98)
        at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:143)
        at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:111)
        at com.android.volley.NetworkDispatcher.run(NetworkDispatcher.java:90)
     Caused by: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2247 path $.products[1].extra
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:226)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:131)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:222)
        at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:41)
        at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82)
        at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:131)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:222)
        at com.google.gson.Gson.fromJson(Gson.java:927)
        at com.google.gson.Gson.fromJson(Gson.java:892)
        at com.google.gson.Gson.fromJson(Gson.java:841)
        at com.google.gson.Gson.fromJson(Gson.java:813)
        at org.wordpress.android.fluxc.network.rest.GsonRequest.parseNetworkResponse(GsonRequest.java:92)
        at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:143) 
        at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:111) 
        at com.android.volley.NetworkDispatcher.run(NetworkDispatcher.java:90) 
     Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2247 path $.products[1].extra
        at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:385)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:215)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:131) 
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:222) 
        at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:41) 
        at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82) 
        at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61) 
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:131) 
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:222) 
        at com.google.gson.Gson.fromJson(Gson.java:927) 
        at com.google.gson.Gson.fromJson(Gson.java:892) 
        at com.google.gson.Gson.fromJson(Gson.java:841) 
        at com.google.gson.Gson.fromJson(Gson.java:813) 
        at org.wordpress.android.fluxc.network.rest.GsonRequest.parseNetworkResponse(GsonRequest.java:92) 
        at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:143) 
        at com.android.volley.NetworkDispatcher.processRequest(NetworkDispatcher.java:111) 
        at com.android.volley.NetworkDispatcher.run(NetworkDispatcher.java:90) 

The response is:

{"cart_generated_at_timestamp":X,"blog_id":X,"cart_key":"X","coupon":"","coupon_discounts":[],"coupon_discounts_integer":[],"coupon_discounts_display":[],"is_coupon_applied":false,"has_bundle_credit":true,"next_domain_is_free":true,"next_domain_condition":"","products":[{"product_id":76,"product_name":".blog Domain Registration","product_name_en":".blog Domain Registration","product_slug":"dotblog_domain","product_cost":528,"product_cost_display":"528 K\u010d","product_cost_integer":52800,"meta":"testingquickstart.blog","cost":0,"currency":"CZK","volume":1,"quantity":null,"free_trial":false,"orig_cost":0,"cost_before_coupon":528,"coupon_savings":0,"coupon_savings_integer":0,"coupon_savings_display":"0 K\u010d","is_sale_coupon_applied":null,"extra":{"privacy":true,"registrar":"KS_RAM","domain_registration_agreement_url":"https:\/\/wordpress.com\/automattic-domain-name-registration-agreement\/","privacy_available":true,"premium":false},"bill_period":"365","months_per_bill_period":12,"is_domain_registration":true,"time_added_to_cart":1607526833,"is_bundled":true,"item_original_cost":528,"item_original_cost_integer":52800,"item_original_cost_display":"528 K\u010d","item_original_monthly_cost_integer":4400,"item_original_monthly_cost_display":"44 K\u010d","item_subtotal_monthly_cost_integer":0,"item_subtotal_monthly_cost_display":"0 K\u010d","item_original_subtotal":528,"item_original_subtotal_integer":52800,"item_original_subtotal_display":"528 K\u010d","item_subtotal":0,"item_subtotal_integer":0,"item_subtotal_display":"0 K\u010d","item_tax":0,"item_tax_rate":0,"item_total":0,"subscription_id":0,"is_renewal":false,"domain_post_renewal_expiration_date":null,"related_monthly_plan_cost_integer":0,"related_monthly_plan_cost_display":""},{"product_id":18,"product_name":"WordPress.com Credits","product_name_en":"WordPress.com Credits","product_slug":"wordpress-com-credits","product_cost":0,"product_cost_display":"0 K\u010d","product_cost_integer":0,"meta":null,"cost":-0,"currency":"CZK","volume":1,"quantity":null,"free_trial":false,"orig_cost":null,"cost_before_coupon":0,"coupon_savings":0,"coupon_savings_integer":0,"coupon_savings_display":"0 K\u010d","is_sale_coupon_applied":null,"extra":[],"bill_period":"-1","months_per_bill_period":null,"is_domain_registration":false,"time_added_to_cart":1607526833,"is_bundled":false,"item_original_cost":0,"item_original_cost_integer":0,"item_original_cost_display":"0 K\u010d","item_original_monthly_cost_integer":0,"item_original_monthly_cost_display":"","item_subtotal_monthly_cost_integer":0,"item_subtotal_monthly_cost_display":"","item_original_subtotal":0,"item_original_subtotal_integer":0,"item_original_subtotal_display":"0 K\u010d","item_subtotal":-0,"item_subtotal_integer":0,"item_subtotal_display":"0 K\u010d","item_tax":0,"item_tax_rate":0,"item_total":0,"subscription_id":0,"is_renewal":false,"domain_post_renewal_expiration_date":null,"related_monthly_plan_cost_integer":0,"related_monthly_plan_cost_display":""}],"total_cost":0,"currency":"CZK","total_cost_display":"0 K\u010d","total_cost_integer":0,"temporary":true,"tax":{"location":[],"display_taxes":false},"savings_total":528,"savings_total_display":"528 K\u010d","savings_total_integer":52800,"coupon_savings_total":0,"coupon_savings_total_display":"0 K\u010d","coupon_savings_total_integer":0,"sub_total_with_taxes_display":"0 K\u010d","sub_total_with_taxes_integer":0,"sub_total":0,"sub_total_display":"0 K\u010d","sub_total_integer":0,"total_tax":0,"total_tax_display":"0 K\u010d","total_tax_integer":0,"credits":1720,"credits_display":"1,720 K\u010d","credits_integer":172000,"allowed_payment_methods":["WPCOM_Billing_MoneyPress_Paygate","WPCOM_Billing_PayPal_Express","WPCOM_Billing_Stripe_Payment_Method","WPCOM_Billing_Web_Payment"],"create_new_blog":false,"messages":{"errors":[],"success":[]},"bundled_domain":"testingquickstart.blog"}

The screen looks like this:

Start with the domain-registration flow and the shopping-cart response at /me/shopping-cart/169844210/?locale=en_US, then inspect GsonRequest.java around the reported parse failure. Compare the products[1].extra response shape with the client model and reproduce the credits-based registration; done means the response no longer fails silently and the flow presents an appropriate result.