Regardless of which car is being jump started, the negative terminal should always be connected to the ground point not the battery. You should have a little plastic guard that clips over the negative terminal that warns you to do this
Please try another code reader, or test the fuses with a multimeter
. Please don't use carista. It'll just lead you down a rabbit hole.
Alternatively were in Bridlington, East Yorkshire and we'd be happy to investigate it for you