We have a bunch of smaller projects with common code that get built and deployed as NuGet packages using AppVeyor’s automatic publishing feature. Unfortunately when these projects were upgraded to use the new default Visual Studio 2015 build worker image automatic publishing broke.
It turns out that that it is required that the .nuspec file is required to have the same name as the .csproj file for automatic publishing to work. I am not entirely sure, but from reading this question I think this used to be a requirement that got removed however the new worker image has regressed to requiring this again. The fix to get these to automatically publish again, was to simply rename the .nuspec.
I have submitted issue 739 to find out if this is still a desired requirement or a regression.
UPDATE: Turns out .nuspec files are required to have the same name as the project. See issue 707 for details. I have submitted a pull request to update the documentation.