My problem is even worse. This just popped up with the 2004 update to Windows 10. All of the options in Projecting to this PC are greyed out on my XPS 8930 and it reports that the wifi card does not support Miracast so I can't turn it off. I never turned it on in the first place and Mobile Connect worked in the past. There must be some way to fix this short of buying a new wifi card which I don't need and only use with Dell Mobile Connect.

I found the problem with my XPS 8930. While there had been no problem with Dell Mobile Connect prior to the 2004 Windows update, so I assume that things were ok before that, I discovered that I had to go to Settings Apps and hit the Optional App button and install the Wireless connection. Once I did that, I set the Projection option to Never and Dell Mobile Connect suddenly started working.