S4c+ The K2 is not activated.

When I activate engines ON, K1 enters and K2 does not.
We saw that from the Chain Run we get 24v to K1, but 0v does not reach K2, and that is 
why K2 fails.

We changed the A81, we also changed the power supply.
And we still do not have that 0v of the Chain Run.
For it to work, it is bridged with the 0v of K1.
Any idea what is happening.