Here's how to look for multiple accounts or to regain access to an account, reset password, etc. I'll also tell you a different way to look for it at the bottom of this posting.
A User ID may be an email address, but it doesn't have to be. It might be only part of an email address, or until recently, it can be anything at all.
To get a list of your User IDs, reset password, and recover account access, etc., you can use the tool at the link below. When using the Account Recovery tool, try using your phone number first if you can still access it. After that, if necessary, then run the tool on your email address(es) you can still access.
NOTE: Before running the account recovery tool below, log out of all Intuit accounts including this user forum, or you might end up in a loop. Then clear your browser Internet cache, close your browser, then reopen it, and go to the link below. You may wish to copy this link so you can paste it into the new browser session.
https://myturbotax.intuit.com/account-recovery
If still no luck after running that on your phone number you can still access and email address(es) that you can access, here's another method:
Go back to the tool again, but this time leave the data field blank, scroll down a bit, then choose the small blue link that says "Try something else"