Your vehicle ECU is just like any other electronic component, and can fail without reason, In this case either a new ECU from the dealer or a second hand one is required (which usually involves other components) to function correctly.
We can at times still recover data from your old ECU so that it can be transfered to another working replacement ECU.
Also, with many non experienced people remapping cars, ECU'scan be left in a non functioned state after a remap, known in the trade as a "bricked ECU" luckily we can try to rectify ths for you.