I really cannot explain why it doesn’t work. Two things that are strange:
1. You measured about 28VAC on slot 2 with the zone wire connected, so that means at the time of your measurement, 28VAC is present between COM and slot 2. I don’t understand how that can’t activate your solenoid — it’s like saying 28VAC is applied on the two wires of the solenoid, and it doesn’t open. This does not make sense.
2. The screen shows the current draw is 3532mA — this is also very wrong, the current draw is usually about 200 to 300mA when a solenoid is active. 3532mA is way beyond the limit.
Something is apparently quite wrong but I don’t know what.