This question already has an answer here:
I am getting the following error while trying to connect to NuGET.
wtf.
[nuget.org] Unable to load the service index for source https://api.nuget.org/v3/index.json. An error occurred while sending the request. Unable to connect to the remote server A socket operation was attempted to an unreachable network [2606:2800:133:f17:19e8:2356:251b:2a9]:443
why is this happening? and why is it using ipv6?
help help
It would be related to your Proxy, you can add proxy settings in your Nuget.Config file.
You could get useful information from the NuGet.Config Reference and Nuget Proxy Settings.
Update:
So you have resolved this issue here:
Nuget connection attempt failed "Unable to load the service index for source"
Am I right? If so, you could close the two cases:)