I had the same on mine, but mine was caused by a cowboy who have replaced my screen, and had blocked the little gutter at the bottom of the screen (under the scuttle panel), the caused a build up of watr around the corners of the screen, and guess what, he hadn't sealed the corners very well !!, i could get a large flat bladed screwdriver into the gap
the water then found its way down to the fusebox.
Remove the fusebox, and get it dry, then replace with a plastic bag over the top of it to stop any further ingress while you find the cause.
As above, also remove the scuttle panel, and make sure the drain hole in the middle isn't blocked, as this can fill up, and eventually will find its way into the cabin.