[om.ibbl.cellfin] OTP not working on banking and wallet apps

Affected app
Name: [Cellfin, Bkash]
Package id: [com.ibbl.cellfin]
[https://play.google.com/store/apps/details?id=com.ibbl.cellfin&hl=en&referrer=utm_source%3Dgoogle%26utm_medium%3Dorganic%26utm_term%3Dcellfin+playstore&pli=1]

Describe the bug
It's the most used banking app of my region. The firebase auth is not working. and app doesn't allow manual OTP input when logging in for the first time. It works fine on devices that support google but I'm using Huawei mate 50 which lacks the good play service. Well, I tried with old and new versions of this microg app(Installed all 3). It does work on most of the apps I'm using. Just some of the banking apps are exception.

To Reproduce
Steps to reproduce the behavior:
Opening the app, giving phone number and pin and they will send an OTP which has to be automatically done.

Expected behavior
It was supposed to automatically accept the OTP. I'm receiving the OTP.
Screenshots
If applicable, add screenshots to help explain your problem.

System
Android Version: [e.g. 12]
EMUI 14.2 (latest version with latest security patch)

microG
microG Core version: Latest and old
microG Self-Check results: All ticked

No repository file or test is named in the report. Start by reproducing first-login OTP on Cellfin or Bkash with the listed Huawei EMUI 14.2 and microG setup, then trace the Firebase authentication path. Done means the received OTP can be accepted without Google Play services.