Hey, thanks for reaching out. This is an odd error that I haven't seen before, so it may take some troubleshooting. I'm not super familiar with Cubase myself, so the steps I'm going to outline might not be 1:1.
Which version of GuyEngine do you have installed?
Does this error persist in a fresh project with an instance of GuyEngine loaded?
This is what I suggest to troubleshoot -
1. Completely remove GuyEngine and all of its components for your computer
2. Open your daw, scan for plugins and make sure that GuyEngine is completely gone and not detected anywhere
3. Reinstall GuyEngine
4. Scan for plugins again
5. Start a new project and open an instance of GuyEngine - if it works, you may have to re-enter your registration key for the 4 main discs.
6. Open your previous project
Let me know if that works - if not, we'll keep working at it!