FIX IOS SIGNUP ISSUE (API ERROR)

Hi, We have flutter app and the backend is in Laravel. We had implemented Firebase OTP for signup and forgot password to verify our users through SMS. Right now, our android application is working perfectly but our IOS application gives error “invalid token” while signup and forgot password for new users.
We are looking for someone very gentle to solve these issues as we have a a bundle of active users.
Thankyou!