I think it's your monitor software. Have you more than one monitor listed in Device Manager? If so make sure that you are using the right one. You'll need a pundit to tell you which monitor to remove! Or/and try reinstall with monitor disc.
AMD Radeon Adrenalin release date, new features, compatible graphics cards
Inside the iMac Pro - Apple's most powerful Mac yet
iMac Pro release date, UK price & specs
Comment nettoyer Windows et optimiser son PC gratuitement ?