Just submitting this to pile onto the numerous reports about problems with AnyNet+ and HDMI CEC.
Neither disconnecting/reconnecting HDMI cables nor disconnecting/reconnecting power to my receiver seems to correct the problem. Only performing a hard reset to the TV via disconnecting/reconnecting power works. This makes me suspect that the fault lies with the TV. I'm hoping that Samsung can eventually provide a firmware update that will solve this.
I have the same issue with my q8fn tv too! that’s exactly how I have been dealing with this issue as well!! I m glad that I m not alone.
I really hope samsung will fix it one day. I have been using the onkyo receiver (rz810) with my old samsung tv for years without any issue.
I am now having this issue too, I have the Q8FN and I bought it last August and everything was working perfectly until 2 days ago, I have my PS4 connected, Shield TV, Xbox One X and the regular One and Fire TV, TV recognised all of them when I first purchased it and everything worked perfectly until 2 days ago when all of a sudden I could not control my Shield Tv so I restarted it and it worked, then I switched inputs to my PS4 and the TV usually turns it on from Sleep Mode but it didn't so I started it manually but I could not control it with my remote, my Fire TV disappeared all together so I unplugged it and plugged it back again and the TV says Unknown source and I tried to do it manually but for some reason the Amazon Fire TV brand is not on the list, the only thing that still works perfectlly with Samsung Anynet+ is my xbox one, I could turn it on from my TV and use the remote to control it, I tried everything mentioned here but nothing worked, the Shield TV would work after I unplug the power from the TV but only until I change inputs and when I go back to the Shield TV it stops working, I am still under warranty so I am scheduling a service, I needed to schedule a service anyway because my TV suffers from Terrible blooming in dark scenes especially if I have game mode on when everything is super bright but if I have it on Movie or Natural I don't notice it, I mean these TVs are supposed to be top of the line, I paid almost 3k for my TV only for it to go down to 2300 a few weeks later.