Open any game that isn't getting up to this resolution, then press CTRL+N.
See if you're landing into a RTX 3080 rig.
#limited 1440p support on Ultimate tier
serene frigate
Now I found out the reason why, then.
Yes, for some reason, a few users are landing into 2080 rigs, which locks them from using QHD and 4K resolutions plus 120FPS.
I, personally, believe that is related to the 4080 upgrade process.
What you can do, is to contact NVIDIA support and try to get some info on it:
https://www.nvidia.com/en-us/support/consumer/
Scroll the page down, and you will find the Live Chat and Ask us a Question links.
Or, in case you don't care too much about the latency, full free to try EU Southwest (Paris) and EU Central (Frankfurt).
No problem.
Hope, once the 4080 upgrade is available, we stop to face this issue.
I also had moments where I landed into the 2080 rigs.
Hopefully. 😅
serene frigate
Interesting. 
Keep monitoring and see if it will remain like that. Hope it does.