I have the same issue.
For the past few weeks, the shared folders I had been using for months in Windows Explorer have stopped working. They now only appear as shortcuts and not in the tree structure on the left. If I click on them, they open in the web browser.
On the other hand, other shared folders that I have been using for years still work perfectly.
Note: in the shortcut of the shared folder that still working, the Status shows a green checkmark and a little figure. When I hover the mouse over it, it says "Available when Online, Shared". However, for the folders that are giving me problems, when I hover the mouse over them, it says "Available when Online, Shortcut".
Update: I just asked the person who shared the folder that is still working to share a new one with me, and it works! However, the other folders still don't work.
The shared folders that are only added as shortcuts and can only be accessed through the web browser were created on Mac devices. Could this be the cause of the issue?