PKI Hub 1.3.1 fixes the following known issue of the PKI Hub 1.3.0 platform.

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

PKI Hub 1.2.0 installations with the Certificate Authority deployed solution do not support upgrading to PKI Hub 1.3.0.

Workaround: Skip the 1.2.0 release and upgrade  PKI Hub 1.2.0 to 1.2.1