Me too, I tried many troubleshooting steps listed here, including removing and readding YTTV as a source, logging into individual network live stream pages and verifying my YTTV provider works and confirmed able to stream off their sites, updating individual channels, still no go. I am down to 64 channels (down from 115 before I updated to the latest version) and most of those channels are the little known ones. All major channels that worked before (e.g. ABC, NBC, BRAVO, TLC, HGTV, etc.) all say notAuthorized. I have sent my logs to support already. Any help would be much appreciated. Maybe let us downgrade to an older version? I think the last time I updated before this happened was in April 2020.
I removed YTTV as a source and re added. Same result.
I manually scanned the missing channels. Still, "not authorized". At the YTTV web page for TVE, I can log onto the channels in question.
I rebooted my MacMini, etc...
What now???
You need to click Support > Submit Diagnostics at the top right of the DVR and email support.
I just set up YouTube TV and am getting only 62 channels--mostly lesser ones. I logged into NBC and have tried deleting, readding, rescanning, etc. several times. Any tips? Thanks!
I submitted my diagnostics almost a week ago, got one email and responded and nothing since. Any updates? It seems to be a bigger issue if multiple are having the same problem after updating to recent versions of Channels DVR. I also wonder if YTTV adding new channels had something to do with it since I didn't have this problem until after they added the new Viacom channels.
Please give us an update or some indication that you are looking into it.
Thanks!
YoutubeTV is now available to log into the Viacom Channels but still says Login Unsupported in Channels.
I have tried Paramount Network and Comedy Central and they worked on my Mac but not on Channels DVR.
Thanks
Downloading the latest version will correct the issue. New as of 7/16/20...
Worked perfect. Thanks.
Can confirm that after updating to version 2020.07.17.0024 today, I was able to get my channels up from 66 to 120, including the new Viacom channels. Thank you very much for fixing this issue!
Did you have to do anything after updating the DVR software?
I rescanned all channels under YTTV. After that, my channels showed 120 instead of 66.
Today I was unable to stream Paramount and VH1 TVE as I was getting an unauthorized location error. I re scanned YTTV TVE and that seemed to work.
I am having troubles signing in. It appears there's a captcha that I need to fill out but there is no way to do it?
Any help would be appreciated.
Iād try logging into your google account from another device in the same location. The captcha is probably a one-time extra security step, so if you complete it on another device that may prevent it from appearing for Channels.
Tried that already and it didin't work 
Are you using a VPN?
Yeah I am since I don't reside in the US.
Managed to skirt it by turning off the VPN, logging in and as soon as it starts to scan for the first channel quickly turning the VPN back on.
Working well now!
Anyone else unable watch or record Comedy Central? I'm getting could not start stream on channels=[6011]: TVE: unavailable in current location whenever I try to access CC via Channels. CC works fine via Youtube TV.
EDIT: I'm running version 2020.08.03.2001 of Channels DVR.
I'm able to access it.
I'm running version 2020.08.12.1854 of Channels DVR
Nevermind, just saw the Hold down UPDATE trick and it updated to a newer version and found the missing channels.
Running, 2020.06.16.1927, on Windows 10. Cannot get VH1, MTV, Paramount and probably others via YTTV, Have removed YTTV and readded, rescanned and nothing. Run auto update and it says I am at the newest version available.
Channels,
YouTube TV
[118 channels]
Am I doing something wrong or is it an issues with the Windows client?