ARC and/or HDMI-CEC are a mixed bag. It may or may not work at all, or it may have some quirks, or it may work great, it's a roll of the dice. And, when you mix the implementations of these features from various brands, you multiply the chances for problems.
So, the first piece of advice is, don't put all of your eggs in the ARC basket!
Have you gone through the configuration routines for both the TV and the AVR? Or did you just try to plug-and-play?