Hook up DVR to Roku TV. Hooked up with Coxial cable from VCR to TV. VCR will run but will not sh

Alas! And I need help, lol. Channels 3 & 4 seem to be gone, for good. I added the Roku phone app and cannot get them there either. Any ideas? My old VCR (which works perfectly) runs on Channel 3 & 4....