I'm having the same problem. I find that if I just click the back arrow the error box disappears and the regular screen displays. I can look at live TV the other features, but I cannot record anything. Particularly bad timing since I'm a Youtube TV subscriber and was going to depend on this system ...

Update: After removing my attached USB DVR drive which was full, no more error messages. Problem solved? We shall see.

This problem began after the recent firmware update.
The firmware update broke HDHomerun on all my Roku devices including my Roku TV and Roku Ultra.
It works on Windows 10 ...