For me, this type of issue will present while the splash screen is showing and the app is attempting to synch data.  If I persist and restart MSFS a time or two, I may get lucky and the program will get through the splash screen and startup sequence and then run normally. Other times, no such luck, and I may wait a few hours and then return to see the program start normally. Must be the servers are flaky, to my thinking. 
Rich

Hello everyone and thank you for your input. Just to clarify I spent nearly a week trying to get MSFS past the initial splash screens and always the same black screen and white spinning disc. In the middle of those splash screens was a dark black square that flashed and had writing also so something weird there. I have forgotten how many times i rebooted the computer both restarts and full shut downs  but always the same thing. So I think I gave it plenty of time to correct the issue. I had emptied my community folder once it would not start and made sure windows was up to date and the x box app. I had worked my way through the Microsoft suggestions until I just gave up trying and decided to uninstall completely the pc steam version. I did look at doing a verify files but was put off by comments that it would initiate a full reinstall and download everything again.  I have not as yet reinstalled the pc steam version as I will wait for Sim Update 11. I did delete all files manually as the uninstall in Steam only uninstalls the installer. My internet connects to everything just fine and i even ran P3d with all the various add ons to check and it was just fine.

So here I am with MSFS fully uninstalled and not a great deal of confidence at the moment that reinstalling will work. I am not technically minded re computers but I am very careful about following procedures. I could understand if i was getting past the checking for updates and it hung doing the loading  but not getting past those splash screens with the flashing black square is something I could not understand and which Microsoft did not even refer to or make a suggestion about.

So thank you all for your help it is much appreciated.

Dave