Register old version of Xojo for XP

I need to compile a desktop app for Windows XP (don’t ask why please).
I have the latest version of Xojo on my Windows computer and also my Mac which uses up my allowable licences.
I installed 2014R3 also on my Windows computer but it won’t allow builds. I can’t use a licence even though I was a licensed user at the time of release.
Anyone know how I can do this?

Contact for help.