Hey thanks for your comment. This is the first I've heard of this issue, so let me see if I can help you!
You will have to register each "disc" one time - but after that there should be no trouble. Try using the "register" button rather than the window that pops up when you start it.
Try this:
- Start a blank project
- Load GuyEngine
- Close the register window without entering your key
- Click the register button
- Enter your key
- Change to disc 2
- Repeat until all 4 discs are registered.
- Test each disc to make sure sound is coming out
- Close FL Studio
Now any project that is using GuyEngine - regardless of number of instances - should be registered permanently.
Let me know if that helps!