I have a couple clustered SQL server instances, 2 on 2014 and 1 on 2008r2. In all 3 cases, I've created a SQL login (server principal) for a domain group, say DOMAIN\SqlAdmins. I grant it the 'sysadmin' fixed server role, for example. (Don't give me a security lecture, that's not the question!)
Now, on my workstation, using my domain account, which is a member of this group, I fire up SSMS. I can log in and have the rights expected.
However. I RDP to the server that's hosting one of these instances, using this same domain acct (which is a domain admin, in this example). If I use SSMS on the server box in this fashion, and try logging in to the instance with Windows auth, it FAILS.
What piece of this puzzle is out of place here?