Battery converter not charging battery

Hi, I am connected to shore power, but the battery converter doesn't seem to be charging the battery, what could have gone wrong? Normally when I connect shore power, the battery converter would send 13v to the battery to charge it. I unplugged shore power today, thinking the battery is charged up ready to go, but nop it's flat with just 6v, no lights :(



I can't imagine this to be a major issue, must be something that is loose or some fuse blown? Please help me trouble shoot, much appreciated! keen to go camping now it's spring time in New Zealand :)