Hi,
Agree with the content shared by Jürgen L.
But that seems to be an ambiguous statement, which does not mention whether the individual certificates(S-ID) are expired or the Certification exam (eg C_TAW70_12) is expired.
Fortunately, till now I am able to login to service market place and Credential manager using the S-ID provided by SAP (and hope it will be continued to be so 
).
Regards,
Vinod