Original Poster says Denon works with Denon remote. Thus the Denon is not the problem.

I have seen this happen on other types of devices and it can usually be fixed with a simple hard reset (unplug) of the unit.

Someone explain to me, Matt, if you could, why a firmware update would ever be needed to correct an IR problem. Now, IF and just IF the receiver can't remember its firmware, and needs a new installation of firmware which masquerades or might even be an update, then that makes sense.

Original Poster says Denon works with Denon remote. Thus the Denon is not the problem. Let me digress to HDMI for a moment: As Brent explained to me recently, sometimes Denons appear to have HDMI problems because they are built to handle EXACTLY the right HDMI signal, and when other components send sloppy HDMI, they won't pass it. Other AVR brands might work in these instances if they are NOT AS GOOD as the Denons and will let sloppy HDMI pass through...so, keeping in mind that a receiver so good that it squeaks when it walks might not be able to deal with wrong signals:

Did the Russound suddenly stop passing the IR signal properly? Well, then, how? Why? And how many IR receivers are there in the system -- is there a room where the lighting, or the bulbs, have changed and that room now has different lighting and an interfering IR signal from the lighting is passing through the Russound?

I just replaced my Denon 3310 with a 3313 and hooked everything up as before. I have a Russound CAV6.6 system that does the IR distribution. I tried hooking the 3313 up with the mono cable from the acc IR out port on the CAV6.6 into the IR Input on the 3313 just like it was on the 3310. That didn’t seem to work so I just put an IR emitter on it and called it a day. While it took FOREVER to get the emitter to “work” but I figured that I wasn’t putting it in the right place. Its been working for weeks without issue.

So today, after literally NO changes the Denon stopped accepting IR at all from any emitter. I’ve tried everything, I KNOW that the emitter works
-I’ve tried new emitters (4 or 5 of them), nothing
-I’ve moved a couple of my existing working emitters off other components that worked, nothing (these worked fine before I moved them and after I moved them back)
-I bought a new mono cable to give the rear input another shot, nothing
-I also bought a stereo cable, nothing
-I used other IR ports on the CAV (known working for other components), nothing
-I tested the ACC port with other emitters and devices and they work out of that port fine
-The system remote and the Harmony both work if pointed at the unit directly (no IR distribution in place)

This WAS WORKING and NOTHING changed, the gear is in the basement and no one was even down there between when it last worked and when it “broke”.

Of course I am leaving for a business trip in the morning and now my wife is going to have to deal with the using the super buggy Denon app to turn the unit on/off, volume, input select….

HELP!?!

Yes, "locally" both remotes (the one that came with it and the Harmony we usually use) work. But I know that the IR distribution does work as it can control the other components its connected to (blaster).

thats the part that doesnt make any sense to me, even if I blast it with a known good emitter (from another component that does work) it doesn't control the 3313, makes no sense...