Are you 100% sure the ATSC3 tuner is available when asking for it? Sometimes when changing channels or turning a channel off, the tuner will "hang" for a bit so maybe it's "in use" (kinda).
Just a theory/thought.
Nah, I'm using this to monitor. Pretty much shows me exactly what's happening. He hasn't mentioned any ports to other operating systems, but if you have Win10 or 11 it's very nice to have. I run it on an old second monitor I have attached to my HTPC/server.
I gave up on my 3.0 channels. Regular ones come through fine and record fine. I may try some of the "fixes" noted above.