Nicehash no longer accurately displays information when connecting to Flypool. This happened when they upgraded their website.
You’ll notice that while it’s showing 100% rejected at the pool, it is not actually being rejected. Your hashrate will go up but it will not show it for several minutes. If after about 15-20 minutes you don’t see a change on Flypool, I would cancel the order and try again.
There’s really no indication that the issue is explicitly Nicehash or Flypool’s fault. One of them is giving incorrect information and your best bet would be to contact each individually to see if maybe they can fix it. I have a sneaking suspicion that Flypool won’t care though.