You must set the inventory, if you want to enable banking.
So when you start up, grab the food you want, e.g. 20 lobsters, then when the perfect stronghold setup window is open, click the 'load inventory' button
this will set the items to bank for, and it will work
here is image:
instead of guthans armour, it will show your inventory, so if you have 10 lobsters it will say "Lobster x 10', but you MUST click the button called 'Grab inventory'