Reset button on Lister Start-o-matic wont reset

Help.................? I have a Lister ST2 Start-o-Matic generator. It failed to start recently because the two 12v starting batteries were flat (- this sets off the red Genset Failed light). Now I have recharged the batteries, but the Reset button will only turn off the Genset Failed for 20 seconds and this stops the generator from working, ( if I quickly switch something on, the generator starts, but cuts out when the light comes on). I have tried replacing all the relays but I still cant get the Reset to work. Any ideas anyone..................? Ray