I would find out what happened with your account. The various levels have specific requirements. Maybe something happened with the various requirements that caused your account to reset. You can check your account level settings to see if something shows an unverified.
Level 1 requires a telephone number. If you changed your number, or if they sent a text that got rejected it would probably cause your account to reset.
Level 2 requires banking information. Same as above. Also, some banks are extra sensitive to fraud activities (chase or citi). Check to see if something happened with your level 2 information since your bank may have issued a fraud alert with coinbase. Level 3 requires photo id confirmation.