by Paul P..
Update:
On further testing, I was able to restore a backed-up flashcard activity from another site where the activity is working (I created the activity, backed it up on the other site, and then restored it on the site where I am having difficulty).
It restored properly and seems to work as it should.
So the issue appears to be with only setting up a new instance of this activity, as the activity does work.
Again, any thoughts and ideas would be greatly appreciated.
Thanks,
Paul