I’m sorry, I didn’t understand this: “The Clipboard plasmoid in my thumbnail box”
There is a Clipboard plasmoid, it seems to rely on Klipper. You can configure Klipper shortcuts to show clipboard items at Mouse Postition - which would work nicely with something like MetaV or MetaB
This would confirm that your clipboard and history are working… and what you see there should be mirrored in the plasmoid.
From there, you can try creating a new USER and log in there to verify there’s a genuine issue, not of your making (like through settings - some folks set clipboard to clear itself).
So no response is really possible - something is wrong with your machine, probably the contents of your home folder/data/cache/preferences need cleaning up.
Something I can say, however, is that Klipper works 100%, but CopyQ did glitch for me last week - I couldn’t get the window to show.
It was a Firefox setting, visible by typing about:config in the address bar. `clipboard.copyPrivateDataToClipboardCloudOrHistory` was set to false; I changed it to true. And it’s working now. I don’t know how this happened; the goal was probably to increase security.