Here's where I posted the original issue...   http://answers.microsoft.com/en-us/msoffice/forum/msoffice_excel-mso_win10/power-pivot-suddenly-unab...

 

 

 

This was the closing response in July 2016:  

"I’ve checked with the related team. Our engineering is aware of this issue and they are working on it. Please keep your Excel up to date.

 

I then noticed that my Surface Book started working a while later