Definitely the same? Because they have quite a range of 1080Tis for some reason. From this page:I have the same video card as you.
How odd.
You reinstalled the latest graphic drivers are doing the firmware update?
Thank you for contacting Nvidia Customer Care. My name is Josh and I will be assisting with your case. We do not have any known issues with using the Rift S and the 1080ti. In our testing it is working just fine. We do not have a Pallet card. This could only matter if the ports they used for the card have issues or are not the same as other cards. It is also possible there is a software conflict. I think what you will need to do here is some more troubleshooting.
If possible to eliminate software conflict. Do a fresh windows install latest updates and just the basics for VR.
To see if the issue follows the card, if possible install the pallet 1080ti in another system and try the rift S. If it happens here then it has to be specific to the card.
You could also contact Pallet directly and see if they know about any possible issues with the ports they have installed on the card.