Connect to TFS error TF31001 object reference not set to an instance of an object
<p>I have a user running VS 2015 trying to connect to our on premise TFS 2015 U2 environment. Other users are able to connect but this user is receiving the following: 
<a href="https://i.stack.imgur.com/gk25x.png" rel="noreferrer"><img src="https://i.stack.imgur.com/gk25x.png" alt="enter image description here"></a></p>

<p>Object reference not set to an instance of an object when trying to connect to the TFS instance. Won't even list the collections. I've verified he can ping the server, he can open tfs web access in IE. Any idea why this is occurring or what log I can look at on his machine that would provide more detail?</p>