Apple Store Rejection due to sign in with apple issue

Our iOS app rejected by apple store saying,

"We discovered one or more bugs in your app. Specifically, your app displays an error message when we logged in via Sign in with Apple. Please review the details below and complete the next steps."

However, our app uses our company’s own account setup and sign-in systems (OpenID Identity Provider). As per the Apple store review guideline 4.8, we don't need to include sign in with apple option.

In our company's own account setup and sign-in system integrated all third-party login (Facebook, google etc.) and sign in with apple too. But in order to sign into the app, specific email should be authenticated from our company user pool. If user (email address) not exist in the user pool, user may receive error message saying,

You don't have required permission

Please help on approval process. Are there any guideline violations?