I am just an amateur in all computers things but I went through many problems before being capable to use rew with my hdmi output.I was able to select umik for input and for output it says not connected or it says hd something. I needed to check the avr hdmi settings.
The problems I had were:
first) related with drivers (intel, nvidia,realtek etc), firmware, software, windows not updated to last version, adobe flash reader java etc must be updated and
second) having downloaded updates or programs (rew or Asio4all) without having stop antivirus,firewalls web protections etc before.
All my problems resolved after that.
Rew is a fantastic piece of machinery and I hope soon be able to post some graphs to get help to interpret all the infos provided.