Can't connect to self hosted instance from Android app

I run a self hosted wallabag instance which works fine (latest docker image, wallabag 2.3.8). I use it from the web, I connected a Miniflux instance to it, it works fine, and I am also using wallabager which works fine.
I wanted to use the android mobile application (version 2.3.0 219) but it fails when trying to connect to the server. I put the URL of my server, my credentials, and I get an error telling me "wallabag not found at this url. Check URL".
I get the following log on the server:

```
Apr 20 09:59:06 melchisedech docker[27419]: 2020/04/20 07:59:06 [error] 254#254: *81 FastCGI sent in stderr: "PHP message: PHP Warning: "continue" targeting switch is equivalent to "break". Did you mean to use "continue 2"? in /var/www/wallabag/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php on line 2636PHP message: PHP Warning: "continue" targeting switch is equivalent to "break". Did you mean to use "continue 2"? in /var/www/wallabag/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php on line 2665" while reading response header from upstream, client: 172.18.0.4, server: _, request: "GET / HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "xxxxx.xxxxx.xxxx"
```

I am using it with Postgres 12 and a Traefik proxy that handles HTTPS.