I’m not sure how it works, but I noticed that in my Plug-In Information, some of the folders there are not needed for Nuendo to actually recognize them. This was occured on my system, and my workaround was this:
I made a list of the plugins that I have. Then, I removed all the folders that direct Nuendo to find the plugins. Open Nuendo and see which plugins appear on their own by Updating Plugin Information. It may not help you as it can always be a different bug, but it worked for me.