I am not sure what is wrong, but my Quick Access in File Explorer in Windows 10 is locked. I cannot pin anything to it. There are no folders in it. If I try and drop a folder onto it (to pin it), I get the Do Not Enter (aka Red Circle with a line) as the mouse cursor.

I've tried various options, reset all options in Windows Explorer Options but nothing seems to give me access...

Where are the Quick Access pinned folders stored in the Registry ?

Any ideas ?