Problem with Uniti Atom ARC Input

Hi all - new poster here looking for help with a strange problem I’ve been having with my Uniti Atom setup that reps have been unable to help me with. I’m definitely a newbee in this area, having gotten into it during the pandemic, so apologies in advance if anything is phrased awkwardly below. My setup right now is:

Uniti Atom
KEF LS50 Meta speakers
Pro-Ject turntable into the Uniti Atom
AppleTV 4K into an LG G2 tv (OLED65G2PUA)
TV out to the Uniti Atom through the HDMI ARC

When I turn the TV on using the AppleTV remote everything in the system turns on (AppleTV, TV, Uniti Atom). But, without fail, the Atom will go to the HDMI input and, despite the TV being on, will say “No input signal.”

I can force it to work by making it re-handshake, typically by going up to the Atom and either (1) switching it to another input, like Analog 1, then back to HDMI, or (2) unplugging the HDMI cable and plugging it back in. It is seemingly random how many times I need to do this in order to get the signal to start coming through, and sometimes I have to reset the entire Atom to finally get it to work. When it does it finally handshake the Atom works perfectly well sound wise.

This issue has also persisted between TVs and ARCs. At first I thought it was the old Sony TV I was using, so I got the LG. Same issue. Then I thought it could be a bad ARC port or something, so I returned the Uniti Atom and got a new one. Same issue with the new TV and new Atom. So this is definitely something going on with the setup in total.

Final note if it matters but generally for music I have a desktop in another room running Roon that I send to the Uniti Atom through wireless. No idea if relevant but thought I’d add.

Thanks in advance for any help.

Tldr; there isn’t a standard for hdmi arc hence some televisions work, others don’t. Certainly it will only work if the tv is sending pcm stereo (hdmi incompatibility not withstanding).
Using an optical connection will remove your frustration.

Thanks, much appreciated. I’ve spent a few hours on the phone with Naim support and provided an extensive amount of detail, including the specific TV model. They were unable to solve the problem. We’ve confirmed TV is on PCM/stereo.

I figured that this went beyond just the typical TV ARC trickiness given that I had the exact same issue with two different types of TVs (Sony and LG), and pointed more towards there being some issue somewhere in the set-up.