Cryptographic Security Platform 1.2.1 fixes the following bug listed in Platform 1.2.0 known issues.

Installations with Certificate Authority do not support upgrading (EDM-19202)

Cryptographic Security Platform 1.1.0 installations with the Certificate Authority deployed solution do not support upgrading to Cryptographic Security Platform 1.2.0.

Workaround: Skip the 1.2.0 release and upgrade  Cryptographic Security Platform 1.1.0 to 1.2.1