WER can't create next round
Sometimes WER goes back and drops a pairing, even if it was correctly entered before. At a WMCQ where I was the SK, we saved the tournament after Swiss, but the next morning we had a different top 8. After a little bit of digging, we found that a result from round 5 had been deleted. Re-entering that result restored everything.
If this is what happened to you, go through each of the earlier rounds and double check that all matches are still recorded. If not, then I don't know what the problem is, but you should still be able to email the results to your WPN rep to have them upload it. That should be your last resort, though.
I hope this helps!