And as fate would have it, even though I have been working on this for hours, as soon as I post the problem here, it suddenly appears as installable in Microsoft Store. Problem solved apparently -- although I have no idea how. 
Hello -- I have seen many posts by users who reinstalled Windows 10 and were then unable to reinstall the My Dell app because the Microsoft Store said their machine was incompatible. My issue is different. I too reinstalled Windows 10 and now cannot reinstall My Dell from the Store, but I DO NOT receive the incompatible warning. In fact, I see the "Get" button, but when I click on it the Store takes me to the My Dell app page but there is no button to allow me to install it. No error message and no incompatibility statement. Where the Install button would normally be is just a blank space.  I would appreciate any ideas or help you could provide on this. Thanks in advance! 
XPS 17 9700 - No Option to Install My Dell App in Microsoft Store