firebase error auth/account-exist
You may follow these steps:-
i. Go to console from your firebase [https://console.firebase.google.com/u/0/](https://console.firebase.google.com/u/0/)
ii. Select your application
iii. Then go to the Authentication option > sign-in method
iv. In the advanced section you can see **One account per email address**
v. Then change it to **Allow creation of multiple accounts with the same email address**