NVIDIA are currently hosting a promotion where new purchases of qualifying RTX cards will also receive a key for the Darktide Imperial Edition.
If you have not received your key for the Darktide Imperial Edition, please contact NVIDIA directly.
The easiest way to do this is by using the 'Ask us a question' or 'Live chat' buttons at the bottom of NVIDIA's Support page here: https://www.nvidia.com/en-us/support/consumer/
More information on this promotion can be seen on NVIDIA's website: https://www.nvidia.com/en-gb/geforce/campaigns/pc-game-bundle-warhammer-40000-darktide-imperial-edition/