If you are having trouble activating your license within the Mocha Application GUI when using the Plug-In version, try closing Mocha and activate using the Licensing section of the Plug-In interface.

The Plugins all have a “License and registration” section you can use to license instead of inside Mocha itself:

In Adobe After Effects, this control is at the top of the effect in the title bar, called “License…”:

In Adobe Premiere, it is the small box in the effect title bar with the arrow:

In Avid, there is a dropdown section at the bottom of the plugin effect:

In OFX hosts it is also in a section called “License and Registration”:

This particular issue presents itself in Mocha Pro 2021 v8.0.0. There will be a patch update in v8.0.1 that will fix the problem of not being able to activate inside the Mocha GUI.