Had the same issue with my TW 9400. It's whatever other equipment the signal is passing through first. If any of that equipment has an upscaler or converter of any kind it will over ride the 4K enhancement in the projector. For example my Cambridge Audio CXUHD Blu-Ray is set to Auto UHD output and 4K Enhancement on the projector is greyed out. When I switch the Blu-Ray to Auto 1080p out then the projector takes over the upscaling duties and 4K Enhancement is selectable. Same applies to any upscaling in your receiver.