Just to expand the community. This happened to me during the Rebuild process (debug mode), I had too many projects (inherited project) in one solution (VS 2019), when I came across Rebuild Solution, it took a lot of time, and I didn’t do it. after the build was completed, the Nuget Package Management menu was turned on as always.
If you need to manage Nuget packages just before building the project, all you have to do is stop building, etc. Your intended menu item is again available.
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