There are three ways to sign in that can point to at least 3 different accounts:
1. Legacy Skype Name (no live: prefixed name) - You sign in using that name
2. Email address (live: prefixed name) - You sign in using your email address
3. Phone Number (live: prefixed name) - You sign in using your phone number.
You can also use the guidance in Forgotten your Microsoft account username to locate all the accounts associated with the information you provide. You will be given hints of all the associated Skype names.
You can also check the contents of your CS_skylib folder located in your Skype for Desktop folder on your system. There may be filenames using your Skype name.
