your forum account is not linked to any cPanel username.
This could be as a result of
`system error
`inactivity termination
`TOS violation
I would say if you could remember you cPanel username a staff member can look up the reason why your account is missing, but you dont't remember it.
So, you can register again. But the registration is slow right now due to system upgrades and dont' forget to login to the forums every 31 days.