Modular Synth Panels

Hello list, 
I just built an Ian Fritz  All-In Envelope Generator kit recently bought in the Bridechamber. It seems to be working OK but the led doesn't blink. 

There is no led polarity indication on the PCB but I tried both ways. I don't know if it needs any jumper.

As you can see my electronics knowledge is not very extensive :-)

Please, any of you could provide any help?

Thanks in advance.

Miguel.