Could not install package 'Owin 1.0.0.' You are trying to install this package into a project that targets '.NETFramework,Version=v4.5.2'

I believe I found the solution.

I ran into the same issue, and it was impacting more than just the Owin package.

I tried flushing my user cache and even uninstalling and reinstalling Visual Studio (deleting any AppData files that seemed related), but the problem persisted.

However, clearing the data in C:\Users\<<UserName>>\.nuget\packages has resolved the issue.