Yup, exactly. I notice the game booting up and even tracking properly but the headset continues inifinitely loading and I get the error.
The SLI is a good point. I had to unplug my SLI bridge to add the vive wireless card in between the two heat-spewing behemoths of a card (comfy :) ) and though I plugged it back in, I did not change any settings when booting up so it's possible SLI mode was reset.
I also have the original Vive, maybe I can try to reproduce on that as you said, but for now it's confirmed only on Pro in a dual 1080 Ti.