The duplication functionality of the individual apps is failing all of sudden today, anyone having this issue?
See if this workaround works for that
Re: Web AppBuilder Developer Edition - Can't create new Apps
Seems like the two issues might be related. I had the same issue as you at one time, but think I started with a fresh copy....next time I plan to try the workaround.
I had the same issue. But it works after renaming the app and removing spaces from app name !
I renamed, then Duplicate worked, so after duplicating I just changed the name back. Didn't have any spaces.