GENCERT gets the ACF00176 message:
ACF00176 Duplicate certificate detected - logonid.suffix
Release : 16.0
Component : CA ACF2 for z/OS
Certificates are stored in the ACF2 database with a record id of logonid.suffix.
Certificates owner by the same logonid(or SITECERT in this case) cannot have the same SUBJDN, ISSUERDN and SERIAL number other wise the 'ACF00176 Duplicate certificate detected - logonid.suffix' message will result.