Octagon SF8008 mini - External infrared receiver not working

Hi Purchased Octagon SF8008 mini recently to install into my caravan inside a cupboard. I purchased this model as It is very compact but more importantly comes inclusive with external IR receiver. I currently run openvix 5.4.009. When I plug external IR in it does not work. also the remote does not talk to the receiver IR when lead is plugged into box. Soon as I remove remote communicates with receiver OK. I contacted the supplier and they confirmed also new stock is the same. I know a long shot but has anyone experienced same issue and found solution. thanks in advance:)