I am not sure if anyone speaks German here. The LED needs connected to the foot switch to work.
I cannot verify any off-board wiring as it is mixed too close with wires of the same color.
My first guess is the the wiring is wrong somewhere (on both builds) but it is too hard to see from the one photo above. I cannot follow the wiring or check all common grounding.
We will need better photos or a diagram to show exactly how it is wired.
Since you wired the LED to the MAIN Board and not the 3PDT Wiring board it still needs a S3, S4 & S5 connection. You will have to make contact over top the wiring board after you figure the Audio issue.
Since both builds do not work it is likely the same error and it would be easier to work on one pedal.
Also did you look at the GUIDES PAGE to trace the wiring yourself?
Does the pedal work in bypass mode?
Also check these guides from the GUIDES PAGE and make sure the wiring is correct and you have checked the entire circuit for proper continuity using your digital multi meter.