Could not connect to the feed specified at '$the-server/app/nuget/v1/FeedService.svc'. Please verify the package source (located in the Package Manager Settings) is valid and ensure your network connectivity.
This is a confirmed bug in NuGet 1.7, as seen in both this NuGet bug report (2066) and this TeamCity bug report (21011). To fix the problem you need to download a newer version of NuGet that contains the bug fix.
As of this blog post NuGet 1.8 isn’t released, but it should be released soon; try updating your plugin to the latest stable version to see if your problem is resolved.
If the latest stable build doesn’t resolve your issue, you can download a nightly build from NuGet’s CI server.
1. Go to NuGet’s CI server
2. Click the link at the bottom to log in as a guest
3. Under the NuGet section you’ll see a couple of options (currently 1.8 and Default)
4. Mouse over the Artifacts link for whichever build you choose (I chose to download a 1.8 build), click VisualStudioAddIn and then NuGet.Tools.vsix
5. Your download should start; let it finish
6. Probably best to close any open Visual Studio instances
7. Run the vsix installer by double-clicking it
Your new NuGet extension should now be installed and your TeamCity feed URL should now work!