What 'expired' actually means
A certification expires when you reach the end of your renewal cycle without meeting its requirements — usually enough continuing-education credits, and any annual maintenance fee the body charges. Expiration doesn't erase the fact that you passed the exam, but it does mean you can no longer claim the credential as active, and employers or compliance frameworks that require it will treat you as uncertified until you restore it.
Most bodies don't flip from active to gone overnight. There's typically a sequence: a deadline, then a grace or suspension period, then a hard cutoff after which the only way back is to re-earn the certification from scratch.