I was having a similar issue. I did an online chat with Microsoft and found a solution that worked for me. Maybe it will work for you too. If not, sorry.
Click "File" in File Explorer
Select "Change Folder & Search Options"
Where it says "Open File Explorer to..." select "This PC"
From "This PC," right-click within the "Network Locations" section.
Select "Add a network location"
This will bring up the "Add a Network Location Wizard."
This allowed me to add network-folder shortcuts to the "This PC" section of the left-side column toolbar.
This didn't really fix the "Quick Access" problem, but it offers an alternative if you were having the same problem as me.