I have Cubase 12 and 13 installed side by side. My Nektar P4 is not working with Cubase 13. It works in Cubase 12 on the same project as opened in Cubase 13. The Midi Port setup is the same in both both Cubase versions. The only difference I can see is that the P4 does not show up in the Devices list of the Studio Setup dialog in Cubase 13.
Cubase 12 Studio Setup Dialog:
So I contacted Nektar support and was able to solve the problem. I needed to upgrade the P4 firmware and run the associated Panorama Steinberg Support script. The firmware/script package was
Panorama_P1_P4_P6_Cubase_Integration_MacOS_10.11_or_higher
Thank you for all of the suggestions. Now back to writing music