There is no command that resets an expiration date.
The certificate will have to go through a renewal process. If the certificate was created by CA Top Secret, you can use a TSS REKEY or TSS RENEW the cert.
If the cert was create or signed by a 3rd party, then you will need to send it out to be renewed by the third party certificate authority.
This is not just CA Top Secret, but with any mainframe security package such as CA ACF2 and IBM RACF.