If you encounter login issues in BGMI, follow these steps to resolve them:
Log in with your Facebook account (link Google Play or Twitter accounts to your Facebook account). Uninstall Facebook apps from your Android device. Log in using only your mobile data, avoiding Wi-Fi connections. Open BGMI Mod APK, turn off your mobile data, then turn it on again to log in with your Facebook account. You should now be able to successfully log in to your account.