Hello @gerhard11 and welcome to the NVIDIA developer community.
I am very sorry to hear that you are running into trouble with your VR HDM and the 3090TI.
Please check out this posting in out customer help section:
https://nvidia.custhelp.com/app/answers/detail/a_id/5382
which you might find useful.
I also recommend you read the thread a bit later on in the discussion, some other users were also successful in contacting Pimax directly about the issue.
Obviously I am sad to hear that you are understandably unhappy with your purchase. Just let me say that the underlying issue, although I cannot share many details, is connected to a very specific part of the DP connection SW and HW where NVIDIA only has limited influence over. And while we have extensive testing in place, including also all the latest VR HMDs, there can always be something that slips through.
I sincerely hope you will get your setup working after talking to our customer service or Pimax’s!
Best of success with your projects!