Just updated my flashed cMP 4,1 and I can't use my GTX 1080 Ti anymore. Usually, I can remote login just after an update to fix driver issues but I can't-do that either anymore. The only solution that has worked, so far, is switching back to the stock GTX 120. The firmware update and 'upgrade' to High Sierra went fine after switching out the GTX 1080 Ti for the GTX 120. Only now I'm experiencing a totally different issue... So I guess we'll have to wait on a webdriver update from nVidia.