(this may help unless someone is familiar with your model and control panel)
If you know the location of your leisure battery, and you have a multimeter, measure across the terminals as you fiddle about with the panel switches when your plugged in. At some point (hopefully) your reading will go up from just above 12v to 14.5 or above. When the battery is being charged its fed that sort of amount in order to charge it. You will hopefully now know what switches do what....finger crossed.
You should see a similar result if you measure the battery and start your van up. First the main battery will read 12 'ish' at standstill, engine off, then 14.5 or so with engine on...then the leisure should also change as the charging switches from main to leisure.
A multimeter should cost under a tenner, and are useful to have, as they can tell you if your alternator is up to scratch and the state of your batteries being charged.
A couple of other things....your fridge may be gas powered too...3 way system. If thats not working Id get it checked by a Motorhome place if your not confident as gas equipment needs to be safe.