Dual output from GTX1080 graphics card to Denon AVR and Ultrawide

Good afternoon,

I'm looking for some help with getting an LG ultrawide monitor (34WK650W) working with an LG OledB7 via a Denon AVR X2500. My graphics card is an Nvidia GTX 1080. Both Monitors work separately however when I turn on 'Extend these displays' the ultrawide gets a blank screen. I've tried changing the resolutions in the Nvidia control panel as I appreciate that both monitors require different resolutions however still no luck. I've wanted to get this working for about 3 years now...thought now with Lockdown 2.0 coming in maybe its time to finally get this working.

Both monitors work fine when the Denon AVR is removed from the chain so I think the AVR is the problem but I'm honestly not sure

Thanks for any help in advance.