Sign in - sing up issue

Hello I have an issue if anyone could help me would be awesome
My app has a sign in and sign up system and both are working and also I set when the user already completed the sign up and goes to the sign in page they have to put their credentials that they used in sing up and app is going to open
The problem is that when they sing in they have to sign in every time they open the app and I already set with the documentation of firebase to get the id token, etc and skip the sing in and goes to the app directly but It only works 2 time for example I sing in for the first time then I close the app and open it again and the skip works complety fine but if I close and open the app again (3rd time) it ask for the sign in again, may you know how to fix it please?