This is an emergency procedure, in case some problem happened during a firmware update and your controller is rended unresponsive; best sympthom, the link does not blink when correctly powered and the fuse is not blown.
So, to anticipate these emergency situations, there is one jumper in the printed circuit board of the Seletek controller to erase the flash memory and hopefully save the day (or night!).
First, remove any attached motors or peripherals.
Now open the box (the screws are hidden under the plastic caps, at the 4 corners, see below the unit).
Then power the unit as usual, no need to hook the USB cable
Once opened, and powered, we have to short that jumper, as shown highlighted in the image (just two small metal pins, they should be shorted using a small screwdriver for example during a couple of seconds).
... and that's all. There's a similar jumper, easy to find, in the Armadillo and Platypus controllers. Its the only jumper in the PCB, and it's always close to the oscillator crystal.
Disconnecting the unit from the power and connecting it again and it will be ready for a full firmware update, a tedious process but this is after all an extreme situation, as explained here.