I finally found the issue. It happens when you generate an encryption key in the project settings. I have no idea why, but it causes this error to happen with your plugin. So to replicate:
- Generate encryption key in project settings. Edit: Then click on all the Encrypt file options, there should be 4 of them.
- Package project for windows. You should get the same error, if not, then also generate a signing key and enable pak signing, then package again, you should be getting the error now.
Edit: It gets even stranger, clearing the encryption key on a new third person template while still having the plugin enabled allows you to package the game again, but on my original project, the moment I use the plugin, encryption key or not, it still causes the issue. I even tried regenerating files and deleting binaries, etc. Hope you can figure this out!