I think Martin is on the right track. I have a 3rd party plugin by XLN audio (electric grand piano). After the windows update, it said I had the wrong computer ID. They explained it on this page:
…and even provided a video on how to fix the problem. It worked.
So I think we’re looking at the OS change as somehow making the computer look unauthorized to the plugin providers. Based on the XLN example, the answer seems to be telling the 3rd party plugins that “you’ve changed computers”. I had to de-register my computer from XLN, then re-register it. Something like that seems likely to work.