There are aircon / refrigeration techs in and around Suva / Lautoka that could surely help. There used to be a guy at Vuda Pt but he got swallowed up by Baobab and disappeared some years ago!
Try asking Yacht Help in Denerau who they would recommend.
Not being cool, it's likely that the problem is something simple, like a dead capacitor or a refrigerant leak, unless this system is dramatically different to others which I would doubt, but I've been wrong before !
Best of luck