errorMessage":"[merchantAccount] cannot be null

I've integrated everything according to the docs but I get a success response saying 'errorMessage":"[merchantAccount] cannot be null'.

let nbPayload = {
opName: 'nbTxn',
paymentMethodType:'NB',
paymentMethod:'NB_SBI',
redirectAfterPayment: 'true',
format: 'json',
};
//Here payload format is specified for netbanking transaction. For different types of payload types
//for other operations, refer https://developer.juspay.in/docs/expresscheckout-sdk

let requestPayload = {
baseParams: {
merchant_id: 'My merchant Id,
client_id: 'merchantId_android',
order_id:'12344',
amount: '10', //eg: "1.00"
customer_id: 'ABC_123',
customer_email: 'test@gmail.com',
customer_phone_number: '78XXXXXXXX',
environment: 'sandbox',
},
serviceParams: {
service: 'in.juspay.ec',
session_token: 'pass client auth token',
endUrls: [], //eg: ["https://www.reload.in/recharge/", ".*www.reload.in/payment/f.*"]
payload: nbPayload,
},
customParams: {}, //customParams are optional key value pairs.
};

EcReactNativeLibrary.startPayment(
JSON.stringify(requestPayload),
(successResponse) => {
console.log(successResponse, 'success');
},
(errorResponse) => {
console.log(errorResponse, 'error');
},
);