I have a project at myname.visualstudio.com/MyTeam/MyProject. I added a contributor to my team, and they were previously able to clone the project. After upgrading to VS2017, myname.visualstudio.com no longer appears in the list of available servers when they click Manage Connections. They can see the code through the project's portal, but clicking on "Open in Visual Studio" results in a message box from Visual Studio saying "You are not allowed to access https://myname.visualstudio.com/defaultcollection". I don't know if it's expected that they should have access to my defaultcollection, since they only have permissions to see one of many projects.
Either way, if they can see the code in the portal, but cannot see it in Visual Studio, it seems like a bug.
I have verified that the same Microsoft Account is being used in both places. It happens to be inherited from the account used to log into Windows 10.
We've tried removing the login in VS then logging in again. It doesn't even ask for credentials due to inheriting from Windows 10.
I've tried removing their permissions to the project then reapplying.
They've tried adding my server address manually. That's not allowed, because you're supposed to select *.visualstudio.com domains from the automatically-populated list.
What next?