There are 2 actions you can make in order to fix this particular issue : resetting "Plugin Loading Cache" and making a new project from the original one. One could be enough, but let's make both of them to be sure !

Make sure Premiere Pro is closed
Start Premiere Pro from your project and maintain the "Shift" key of your keyboard maintained. A dialog should be opened : tick the "Reset Plugin Loading Cache" checkbox and click Ok
Once your project is opened, create a new empty project. Copy everything in the original project (from the root bin in the Project Panel) and paste it in the new created project. It should make a perfect copy of your original project
Close Premiere Pro
Launch Premiere Pro and re-do the same trick to "Reset Plugin Loading Cache" (by maintaining the "Shift" key while launching Premiere Pro)
Finally, launch the PlumePack process
If you have any issue remaining, enable the logs at the bottom of the panel, reproduce your issue and send us the logs following yellow guidelines at the top