My log was showing a drive with increasing errors so I pulled it and installed a new 6TB drive. It appeared to accept the drive and started rebuilding the data. After about 7hrs, it reached 100% rebuilt and then said it was degraded. I tried to log into the portal and see if I could see what was wrong but after the login window it said it was unreachable. The LED for the drive was red. I did a manual reboot and then the RN said it could not reach the server. I rebooted a couple times and now it does not say that but I still can't connect through the portal and the shares are not there. The menu on the front says there is no data on the drive but there was over 11TB data before the rebuild.
I see you have an open support case. With an open support case it would be best to provide this info directly to the support agent. I have added a note to your case to let the agent know the update you've provided here.
Multiple disk failure. If you have more than 1 disk with errors, you should not issue resync; instead, clone the bad drives and then start up the chassis again. Or, clone the worst disk, hopefully it turns out okay, then try to resync a new disk into the array.
