Same here.
I think I found the solution. I'm trying it now, and the app is back in "Waiting for Review". I'll try to remember to update this post with the eventual outcome.
You need to cancel the current submission first. Do this by:
- Going to the app that's in limbo (with the dimmed "Add for Review" button)
- Tap "App Review" under "General" on the left
- For the stuck item under "In Progress", tap "View" on the right
- On the following screen, tap "Cancel Submission" at the bottom
When I did this, the "Add for Review" button became highlighted and I was able to resubmit. I got the usual emails that the status has changed all the way to "Waiting for Review".
Fingers crossed!