fomo does not have a password, and you never type an email address into fomo. You sign in by choosing Apple or Google, and your fomo account is tied to whichever one you chose when you signed up.
The email on that Apple ID or Google Account is your account email.
To change your password, update it in your Apple ID or Google Account settings. That change carries over to fomo on its own, because Apple or Google handles your login, not fomo.
Your account email is the email on the Apple ID or Google Account you signed up with, so changing it happens there too. Signing in to fomo with a different Apple ID or Google Account does not move your account. It creates a new, separate fomo account with its own wallets.
If you are having trouble signing in, make sure you are choosing the same Apple ID or Google Account you originally signed up with, and check that your phone's date and time are set to automatic. If you still cannot get in, contact support.
If the Apple ID or Google Account you signed up with no longer exists, fomo cannot attach a different login to that account, and support cannot override that.
Contact support with your fomo username and the email you originally signed in with, and we will escalate the recovery to our login provider. They decide whether access can be restored, so we cannot promise an outcome or a timeline.