I am unable to connect to the web gui. I can ping the address and I can ssh into the server as well. Looking at the log there was a brief power failure but the UPS kept it running. I tried to do a shutdown -r and in the log after the shutdown message, it said switching to runlevel 6 then it said Trying to re-exec init. That was the last entry. I'm running the current version of UnRaid.

If the server is still on after shutdown -r you'll need to force a reboot.

I tried the reboot command but that didn't work either. Do you mean do a hard boot or is there another command I can use?

The reader's Digest version is that the motherboard lost connection to the USB UNRAID boot drive.
Following tee-tee jorge's advice, I did a hard reboot. However, after a few minutes, I couldn't ping it and my router didn't show it connecting.
I then connected it to my second monitor and connected a keyboard and did another hard boot. I went into the bios and discovered the priority boot drive was not the USB drive. In fact the USB drive was not displayed at all. So I powered the server down and removed the UNRAID USB drive and connected it to my Win desktop. I did get a brief message that there was a problem and I should do a quick scan of the device but I ignored that and went to see if I could see the files. I could so I plugged the USB drive into a different USB port on the NAS server and applied power. I went into the bios and now it found the USB drive. I set it as priority boot and closed. The server rebooted and now UNRAID came up. I was then able to connect to the Web interface and start the Array. It is currently running a parity check. But otherwise it appears to be OK. I have to conclude the problem was with the motherboard and not UNRAID. It may have had to do with the power interruption yesterday although the UPS did kick in briefly. I hope this helps anyone else who runs into a similar problem.