TFS source control - new files not automatically detected as pending changes

Click <Detected: x add(s), x delete(s)> : in the source control explorer then select the file to add

Before unbinding and binding your solution try his:

1. Go to Source Control Explorer
2. Click the "Add Items to Folder" (the one on the left of the red cross)
3. Select the items you want to Add and follow the instructions on screen

That's all

I would unbind and rebind the problem project and try again:

To unbind a solution or project from source control

• In Visual Studio, open Solution Explorer and select a solution or project to unbind.

• On the File menu, click Source Control, then Change Source Control.

• In the Change Source Control dialog box, click Unbind.

To bind a solution or project to source control

• In Visual Studio, open Solution Explorer and select a solution or project to bind.

• On the File menu, click Source Control, then Change Source Control.

• In the Change Source Control dialog box, click Bind.

• Select the database and location to which to bind, and click OK.

• Click OK.

You might need to go to Advanced to find the Change Source Control option

https://msdn.microsoft.com/en-us/library/0eh3790h%28v=vs.90%29.aspx