Register a new user or find a user account that you have access to , and then in the database set the administrator value for this user to 1, and restart Traccar service.
Event easier option is to set web.serviceAccountToken
in config file, login with that token and register a new admin user.
I accidentally deleted the admin user (the first user that was created). Is there any way to recover this user or recreate it with the same privileges it had when it was initially created?