Visual Studio isn't tracking changes, or checking out files from source control as I edit them

Right-click on your solution node and go down to "Go online". For various reasons visual studio can mark your solution as tracked by source control, but "offline". It is still tracking changes behind the scenes waiting for you to go online again. After doing this my pending changes window populated and all is normal. I figured it was a simple setting somewhere.

I found an interesting setting under File > Source Control > Advanced > Change Source Control.

If I bind the solution and project to my source control server (unbind first if it's already bound), then suddenly it works! Saving a file automatically checks out the file and tracks changes.

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Edit: this seems like a bug in Visual Studio. If this workaround helps you, it would be awesome if you create a new issue at https://developercommunity.visualstudio.com with your Visual Studio version info, so that the dev team can fix this!

Go into source control bindings (File->Source Control->Change Source Control) - you may notice only the project is bound - not the solution. Select the solution, click Bind.