Crumar Perfmormer Issue

Hi guys, I’m new on this forum, just discovered it and it is great.
Wondering if you can help me with a repair.

I’ve an old Performer by Crumar on which I replaced/adapted the brass switch which was broken. Now seems everything works fine except the fact than when I engage the switch no sound is coming from the Strings. If I disengage the brass the strings come back to life.

I did a check on the service manual but I’m not so expert and I cannot find where the problem lie. Any tip ?