VLC doesn't detect tuner. How to configure?

[Mugsy]

I have a PCIe-based Hauppauge WinTV tuner card in my computer. Up until today, it worked fine in Ubuntu 20 using Plex.

SO, I went looking for another app. I read VLC can display live TV from a tuner card, so I followed the online instructions, executing from the terminal:

w_scan -c US -X > channels.conf

...which appeared to work. Dunno. Then I opened VLC and clicked "Media | Open Capture Device", changed Capture Device to "TV - digital" with "tuner card" preset to "dev/dvb/adapter0" (thru adapter 3.) Everything left at defaults, click Play, I get a line bouncing back & forth, but nothing happens.

I tried all the other options under "Delivery system" (DVB-C, etc) but they all had no effect.

Is there something I'm missing? Any help is appreciated. TIA.

[Rémi Denis-Courmont]

Check the logs, but it looks like the tuner fails to lock in to anything.