Ok here it is in 4 screenshots.
1 - I imported a image into a Collection "LRTest2." You can see the image and that the Collection is selected.
2 - I created a virtual copy.
3 - I switched to a different Collection and back. The virtual copy is gone?
4 - I created a new virtual copy and you can read that it says "Copy 2" so LR knows there is another copy but doesn't display it?
Ok I think I figured it out but will test somemore to confirm.
After importing images into a Collection, I'm guessing that previous versions of LR used to automatically select the Collection that was created during the import. It leads you to believe that as your images all show up but what I discovered after answering your request for screenshots that the new Collection was NOT selected and the VCs were being created in the All Photos (I guess location??). Until you left the current quick collection or whereever, the VCs showed up. Now I can see that the Collection is not automatically selected during the import process and either I was lucky before 3/6/21 or an update changed the operation of LR?
This lead me to assume they were gone as they didn't show up. Now I need to do a global search for the VCs and see if they are indeed somewhere else. Assuming this is my error and now that I know to explicitly select the Collection after creating it, my problems will be solved!