pdf viewing disappeared in Windows 10 file explorer preview

Hi,

Up to Two days ago I could see PDF files in ms file explorer preview window, in Windows 10, worked just fine..
Auto Update occurred yesterday?? made Edge the default viewer (not what I wanted) and then could not see pdf file in ms file explorer preview window anymore.
Made Adobe Acrobat my default program to open PDFs, that has come back OK, but still cannot see PDFs in preview pane..
I need PDFs to be previewed quickly without opening first!!
Why, how do I reactivate that functionality?

Please help.

I didn't find the right solution from the Internet.

References:-
bit.ly/2khwxSM
Web Video Company

Thanks