SOLVED IT FOR YOU!
The problem is there are many types of HDMI to displayport cables.. ones with an ACTIVE CONNECTION and ones with direct cable. So you see the display port must be converted to HDMI signal and format. To do that there is an ACTIVE cable required which uses powered sort of capture card type stuff that then outputs the signal a second time.. BUT like many lousy audio visual companies and their receivers it often will not resend/transmit freesync as it introduces TERRIBLE latency. Freesync disables and it adds like a second vsync buffer. These cables start at about closer to $50 as they've got a little uhh converter chip and almost all of them on the market DP to HDMI are decades old HDMI 1 not 2.1 and will only do up to 1080p 30hz if you're lucky its lousy.
But worst of all often times the cheap ones adaptor is very very non compliant and non standard and zero specs.. so it doesnt talk well with VESA standard formatting and the EDID and i forgot what else its called the uhh device identifier handshake the monitor uses to notify your GPU or the receiver or mobile phone via the HDMI or displayport or whatever thunderbolt has these uhh little sort of tables of info that are supposed to have like TV broadcasting global international standard rows and values and resolutions supported.. they often have blank or modified ones or pretend to be better than they are.. also if you dial the resolution higher than it can go or refresh rate or try to use HDR or some other features it almost always never works unless you spend like hundreds on some mythical probably a fake but hopefully isnt one on amazon or some other website and cant tell if its a cheap fake one being marketed as a more expensive one.. for years i never saw any HDMI 2.1 ones from DP.. if you just want to output audio to a second receiver then go ahead and mix and match some DP to HDMI.. otherwise ONLY EVER USE all display port to display port or all HDMI to HDMI.. and always whenever possible unless its for low res word processing never ever try to GAME or high quality 8k TV or whatever off one of those "convert the port type to another port type cable"
because it massively lowers colour/imagequality and performance and bandwidth and resolution and refresh rate.
few years back i bought like 3 of them and 1 died in a day and another developed an issue where the colour seemed to flicker a little paler once in a while not sure .. i tried different brands too. searched online read up on it. AVOID LIKE THE PLAGUE
Also keep in mind if you use HDMI and DP ports on the one card at the rear they interfere with each other and limit and lower quality and performance and your max resolution/refresh rates may decrease slightly at the highest colourspaces and HDR/etc bandwidth use may vary.. your audio quality drops too. So in your settings menu in windows go to sound then more sound options and when a classic style window pops up with audio devices for output disable all the inputs and outputs not in use for audio it improves quality. consider disabling mic/recording stuff when not in use too. You should right click and configure audio quality there too. But with both HDMI and DP rear ports at once theres a sharp decline in performance as they're both different outputs/speeds/clocks/ on the one BUS type thing if u get me? Maybe even when trying CLONE display output mode too though that always does help rather than extending. But i get that for work you use them to extend for more desktop real estate for different apps and documents.
Just ensure whatever all 3 monitors are you set them all to the same refresh rate and same resolution even if extending and not in clone mode because of the way the Vsync buffer of windows works so when you play back a video file you can drag from one window to another while its playing.. this would still work but you'd be 120hz on one display and 144hz on the other display means the separate buffers and timings and stuff dont mesh well and you will have stutter or a sort of lag or delay jitter and it feels awful in many cases where the display isnt running off hardware low latency freesync throw frames out fast as they're served up.
