The thermal fuse has melted due to being turned on without the plates fitted, the manufacturer does not supply these as a spare part, your solution is either bypass it or replace the unit, the fust is under the bottom plate inside a heat protective heat cover one of the wires.

I'm not sure, but there is probably a thermal fuse which has blown. These are very difficult to acquire and sometimes very difficult to install (they can't be soldered -- you have to use a crimp connector).

The fuse is about the size of small glass fuse and has a wire on either end of it and it's connected in line with the hot wire coming from the wall outlet.