I started getting this in VS2015 on one of my
machines. I had an additional package feed on myget which constantly asked me
for credentials and failed even when entering correct credentials.
What helped
me was clearing the nuget cache and config by deleting these two nuget folders:
- %APPDATA%\NuGet
- %LOCALAPPDATA%\NuGet
After that I restarted Visual Studio and added my
custom package source again.
