When you first joined, you signed up using one specific method — Sign in with Google, Sign in with Apple, or Sign in with email — and you'll need to use that exact same method every time you log in.
If you choose a different option from the one you originally signed up with, the app treats it as a brand-new sign-up and creates a new account. This will trigger a "phone number already associated with another account" error message — your phone number is already linked to your original account, so it can't be used again on the new one being created.
To fix this:
Go back to the sign-in screen and tap Get Started
In the top right corner, you'll see a Log out option — tap it
You'll be returned to the main sign-in screen
Choose the same method you originally used to sign up
You should then be able to access your existing account
If you're not sure which method you originally used, try the others one at a time — and if you're still stuck after that, let us know and we'll help you from here.