There are two common reasons this happens.
You are using the wrong login method. If you created your account using Facebook, Google, or Apple, you can only log in with that same account. KAYA cannot reset a password for a social login.
Your account may have been deleted. If you see an error that says "Email already exists" when creating a new account, or none of your usual login methods work, your account may have been deleted previously. Your climb data can typically still be recovered.
If neither of the above resolves it, submit a ticket to KAYA support and include your KAYA username and the email address associated with your account, so the team can locate and restore access quickly.