No MOH on transfer

Hi there, I have googled and searched my heart out so if anyone can help.

I have a friend that has FREEPBX (PBX Firmware: 2.210.62-6 )

All is working OK so far, if he places a call on hold they get his custom music on hold, no problem, but if he uses the transfer button the caller gets silence rather than the MOH.
I have tested this with mu own (very old) trixbox and I get MOH on hold and also on transfer there is music.
I have had a look through his setup and I can’t see where this would need setting and as I am no astrix expert in any way shape or form, I would really appreciate some help.