Hello,
I had the same problem 4 days ago when new version 2.63 was rolling out. After few hours this problem disappeard but today it came back and it doesn't allow me to work with my project at all.
So here are conditions when this error appears:
- MIT app companion 2.62u and 2.63u version used (didn't checked other)
- Project is started in emulator or phone via USB
- Already started project or even completely new blank project
- ANY extension added to components (after importing = no error, after dropped to project = error)
- even tried with new mit app inventor account =same situation, error
So everything is OK as long as I use built-in components like button, label and so on. I tried clearing cache and data files of MIT app companion = no effect
I have Android 10
EDIT: So I tried again, and now everything working OK. So the problem exists, but it is active randomly (for now I don't see condition that decides if this problem is active or inactive).