This can be a frustrating process that usually ends with contacting the product support agents.
To
find out, sign out and go to the sign in window, the click on forgot user ID or password then choose to have it emailed to you.
This will have an email sent to your email with a list of all the user IDs connected with that email account
The Email you receive will have a link to reset your password, under that will be all the user IDs connected with the account.