Notarizing Macintosh plug-in for Photoshop

No versions of Photoshop will be able to run non notarized plug-ins in macOS 10.15.

Plug-ins may appear to be loaded when looking at the Photoshop system information but when they are excecuted from the menu they will fail to load. It is very important for developers to notarize plug-ins.

Notarization gives users more confidence that the Developer ID-signed software you distribute has been checked by Apple for malicious components. Notarization is not App Review. The Apple notary service is an automated system that scans your software for malicious content, checks for code-signing issues, and returns the results to you quickly. If there are no issues, the notary service generates a ticket for you to staple to your software; the notary service also publishes that ticket online where Gatekeeper can find it.

See this for more information: Notarizing Your App Before Distribution