If you signed up for 1SE using your Apple ID on an iPhone, your account may not have a password yet. Apple Sign-In also uses a hidden email address, which can prevent signing in on Android. You may receive the following error:
Follow the steps below to access your account:
On your iPhone, open Settings and tap [your name].
Tap Password & Security.
Tap Apps Using Your Apple ID.
Select 1SE and note the email address linked to your account.
On the 1SE sign-in screen, tap Forgot password.
Enter the email address from Step 4 and reset your password.
Open 1SE on your Android device, then sign in with that email and your new password.
If you don’t receive the reset email, check your spam folder or look for an Apple private relay address (@privaterelay.appleid.com).
Still stuck? Contact 1SE support, and we’ll help you get back in.
For additional information, here's a helpful article by Apple on this feature: https://support.apple.com/en-us/HT210426.