Also note that TVE sources such as YTTV or Philo etc....u will not get ALL channels that that streaming services , as only some of them have a TVE feed that channels can use.
SO for many networks, like A&E, Nick, Smithsonian, Discovery Family etc, u still have to use the providers app to watch the channel.
Ok, then why would I have only a Shield and use YTTV? That seems to be defeating the purpose. I got the shield because I knew it could host both apps, but what I hear is it's not fully functional if I use my chosen provider of YTTV.
U would use the YTTV app in this scenario, to access YTTV.
U would need to use a separate compatible server device to host your Channels DVR server software, if you wish to use YTTV as a TVE source.
If your only option is to use the Shield as sever and client, then you will need to use a different TVE source, there are many supported.
Not sure how much more clear we can be about this to you.
As been pointed out previously, this is the one incompatibility issue with using the Shield as a server.
I suggest u setup Channels back onto a dedicated computer. U dont need anything with that much power, so u can get something pretty cheap.
There is existing threads on this topic and YTTV as a provider. U can use the search feature to find them. The other providers, like Philo, Fubo, etc, most provide the same or similar TVE channel access as YTTV
Has anyone heard that Xfinity TVE is now suffering the same fate on the Shield as trying to use YouTube TV? Reason I ask is that I am at my wits end trying to get my Xfinity TVE to authenticate again using my Shield's Channels DVR server. 
Believe me when I say I have tried everything suggested as far as rules and then some, and I mean .........EVERYTHING.......to get it to work! It has come close, but that was a week or so ago where it initially logs in and gets up to (at most) channel 93 out of a possible 197 and then just hangs. Lately for the past week it won't even do the initial login authentication to start the channels scanning. Here is all that has been posted in the log every time I try now. The only thing that changes is the login ID because I try them all, including making new ones many times:
2020/03/10 23:52:07.743864 [TVE] Auth starting for Comcast_SSO as ChannelsPlusDVR
2020/03/10 23:52:07.755229 [TVE] action=auth mvpd=Comcast_SSO requestor=nbcentertainment
And below is all it shows in the "Activity" section of the Settings Menu, and it will stay forever until I turn off and back on the DVR Server:
"Verifying login on Xfinity"
After thinking it over today, as much as I hate to do this, I may just stick with the Youtube TV app for everything from here on out. I will miss out on those things I love about Channels DVR but I don't want to setup another computer just to run it. I am trying to simplify my home network.
Maybe if the Terramaster I own would work, but I don't have too much confidence in it since it's pretty under powered.
I didn't read all the replies so maybe what I am going to say has already been said. I have had the same problem! I have found that I have to delete You Tube TV and then reinstall it on TVE and everything works fine!!! I almost seems that You Tube TV looses its connection with TVE and needs to reestablish the connection!