Issues about y-axis homing

I own a Stepcraft D840, to which I applied the performance kit for the Y axis.
From one day to the next, homing gives an error on the y axis, activating the non-resettable signal with the "reset" button.
I checked the operation of the limit switches "by hand".
For the x axis everything is OK: by pressing the switch, in "diagnostic" the I12 indicator turns green, and the six central indicators (X-Y-Z limit -, X-Y-Z home) turn green.
For the z axis everything is OK: by pressing the switch, in "diagnostic" the I12 indicator turns green, and the six central indicators (X-Y-Z limit -, X-Y-Z home) turn green.
For the y axis: by pressing the two switches, in "diagnostic" the I12 indicator remains off, and the six central indicators (X-Y-Z limit -, X-Y-Z home) remain inexorably off.
Testing the continuity of the two switches with the tester, with the switch turned off there is continuity, pressing the microswitch interrupts the continuity (as it happens, among other things, for the switch for the x axis and for the z axis switch).
What other checks can I do?
Could the control board be faulty (which, since I installed the performance kit, is different from the standard one, supplied with the original 840 package)?
Thanks in advance