Check the battery connections first. They have a tendancy to be loose from the factory/dealer.
If tight, check the 30amp fuse in the fuse box. It may be loose. The fuse box in these things are junk and are the root cause of many problems. Make sure the fuse is installed tight.
If the problem persists then remove the clips from the back of the fuse box and install a watertight, inline 30A fuse holder.
