I wouldn't change the drivers as it is a new laptop so it will have the correct drivers already, it is a Dell.
I have a new Dell XPS desktop (with an nVidia graphics to the Monitor via HDMI (no audio)) and it is much better than my ASUS laptop, & old Acer Desktop which frequently hiccup as ASUS & Acer mess with the default Windows installation so updates etc. often misbehave.
HDMI communicates with the 'target' device via a datalink. The Audio & Video are all part of the same digital data stream, separate to the device datalink. So your AVR should route the Visual to your TV and the Audio to the AVR speakers. So maybe it isn't seeing your laptop as an Audio/Visual source, just Audio. It maybe seeing too high a Video resolution for it to pass through, hence try reducing the video to a lower resolution. My feeling is its something to do with how your AVR is seeing the laptop HDMI data stream.
Got sidetracked doing other things. Yes, I will try the resolution. Honestly, I had tried it last night, but I'm pretty sure I didn't reboot laptop and AVR. So, I will try that again, with complete reboot.