RDP Protocol Error 2056

[dst]

I can't tell you why - we found that solution in MS forums...

Delete the regkey on the server where ASG-RD is installed

This solved the issue.

And for those who dont know this registry value is used to license RDS on a device license basis. If you don't use this I suppose it shouldn't be a problem deleting it.

https://social.technet.microsoft.com/wik...ified.aspx

EDIT:
Thought I mention this just if someone has the same problem as me. You also have to delete any roaming profile you have on the specific user, I assume it's somewhat stuck a setting in there also.