APM RDP Remote resource cannot be reached

 14.1.5.2 with APM

Hi, we have APM confiugred presenting native rdp to users. we have serval hundred users using this on a daily basis without issue, but we now have 3 users who cannot launch the rdp session and get a windows error popup "Remote resource cannot be reached". We know its related to the workstation because that same user can use a different workstation with their same accoutn and it will work.

When I packet cap on the F5 I do not see the trfafic hit the F5, so again 100% a windows issue rather than F5, but wondering if anyone came across this and know a solution? remote desktop works fine for them to other local servers etc, I cannot see anythign in eventviewer that would indicate why its failing, the cert installed on APM is a CA signed valid cert. An activeX rdp icon does work for them, but its difficult to use since it requires a few browser hacks.

Any help would be great