You are not a member of the Remote Desktop Users group. You may have been at one point, but you've been removed. The only time you don't have to be part of that group to RDP to a server is if you are a member of the Domain Admins or Enterprise Admins group.
I run into this a lot at my work, if you aren't a Domain Admin you have to have specific rights to RDP into a server. You have to be part of the Remote Desktop Users on that servers group policy.