Translation:I am a professor. I am not clever though.
You've probably already had this answer for a while, but for newer users like myself, I thought I'd answer because I've been keeping track of this error after asking a superuser about the same a few days ago:
The mobile app's coding allows it to accept bubbles with hyphens, but the desktop/full/web site does not. So it's a consequence of the Gàdhlig course's designers having employ work-arounds for a bug in the system that Duo's developers won't fix.