@Nic2032 

I have the A7 v5.0   Firmware 1.0.16 build 20201029 rel 43238(5553)

There is a firmware upgrade available to 

1.1.0 Build 20201120 rel.50399

I'm wondering if that is the version you are on?

I have a pi that works great for DNS.I do have it on a laptop with Ubuntu 20.

Assuming you are on the same ISP since before this started.

Not sure what else would be going on. 

Thanks, Jon

@dero 

I stand slightly corrected. I have my dns settings in DHCP Server area set to my local pi.

dns settings in Internet / Advanced were set to default (from ISP).

When I try to change them, it says DNS server IP address and LAN IP address cannot be in the same subnet.

So, it won't let me change it.

I'm not sure how much DNS settings matter here as opposed to the settings in DHCP, which works well.

Sorry for the late reply. I don't see whether you found a solution.

I have a similar situation, and although it worked for months with no trouble, it has given me a fit the last two weeks. My LAN has an ATT Gateway (modem/router/AP). I disabled the WiFi in it and added my own router/WiFi (a Deco M9 plus). My Pi-hole is plugged into one of the gateway connectors, the Deco into another. The ATT network is 192.168.1.x, and the Deco network is 192.168.0.x. In the Deco DHCP settings I have told it to notify all clients to use the DNS at 192.168.1.253 (the Pi-hole). All the devices on my LAN (except the ATT router and the Pi-hole) are in the 192.168.0.x network.

The Deco doesn't want to permit you to assign the DNS to the same network it uses; there is a security risk in allowing that. You could find a way to make the Deco accept it, but it will catch the problem sometime that's not convenient and give itself a new network address, breaking the assignments (such as the Pi-hole) and everything will be down until you can get back into it and change the settings. (Getting back in is difficult because you need to use the app, which needs to confirm a password from the internet, which is not working without the DNS. It can be done, but I don't want to have to do it often).

The only drawback to putting the Pi-hole between the Deco router and the ATT router is that the Pi-hole no longer gets true client IP's and the log shows all requests coming from the one IP of the Deco router.