I don't know much the about custom token as you are using custom token to authenticate. But if we are coming to the firebase authentication, the id token issued by firebase has a lifespan of a maximum of one hour. After that the firebase will issue a new id token using the refresh token. I think your id token is getting expired and it is not getting issued again.

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The Firebase ID tokens last for only one hour. As you are using a custom token, if you want stay authenticated beyond one hour you will need to use the Firebase Auth REST API. So you will have to make an HTTP request to get an ID token and a refresh token from your custom token (check the Exchange custom token for an ID and refresh token section). Then, you will just have to refresh the ID token every time it expires (check the Exchange a refresh token for an ID token section).

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