Make sure you're always logging in the same way. Remember, if you usually sign in with Apple or Google, you won't have a password set.
If you've logged in and it looks like a new account (with no charging history or payment methods in place), try logging in another way as that might be what you did originally.
If you've accidentally created multiple accounts, worry not! Just pop us a message with details of the accounts and we'll do our best to sort it for you.