GTubber

Hi guys, I have a Balboa MGS504SZ Control box with a VL620S topside panel, button for jet has broke. Tried to replace with a VL406T as told this would work with control boxes ending SZ. Installed and got the code 1888, communication error. Looks like its near on impossible to order a VL620S from anywhere. The VL620S is from a South Sea Spas and only has Jet & Light buttons. First question what is the meaning of a duplex topside panel? I've noticed dipswitch 3 for duplex panel is off but the VL406T is classed as duplex. Second question, what does the M stand for on the control box? told this could be that it has its own designed software so not control panel with work except a South Sea Spas panel? TIA