Recently encountered a problem where i had installed XenDesktop 5 SP1 and when i tried to point to the licence server i received the following error:
“The License server found at this address can not be used for this version of XenDesktop”
This threw me a bit as the environment i was working in had a full platinum licence so there should not of been any problems. The solution to this problem luckily is quite an easy one. It seems that to licence XenDesktop 5 SP1 you must be running the latest version of Citrix Licence server which at this moment in time is version 11.9. As soon as i installed that i was able to register with the licence server ok.
You can download the latest version from here: https://www.citrix.com/English/SS/downloads/details.asp?dID=1349861&downloadID=2311724&pID=1679389 (you will need a Citrix account to access the download)