I recently setup GitTfs at work because, while working on a cross-platform mobile project, my co-workers and I were beginning to have severe code conflicts using TFS (imagine that).
One of the stumpers I ran into while setting it up was just the simple act of cloning the TFS repo into a local Git repo. The typical clone command is:
git tfs clone http://tfs:8080/tfs/DefaultCollection $/Project1
This is supposed to work beautifully. I, however, was getting this:
"Sequence contains no elements"
As it turns out, none of our project folders in TFS were not actually branches...they were folders (duh!).
So, via Team Explorer (or whatever other TFS interface you use), we had to convert the folder to a branch. A very simple operation, really. After that the GitTfs clone command worked perfectly!