Craftsman LT2000 won't turn over

[Bitterhermit]

Craftsman tractor 917.273130. Turn the key and nothing happens. Battery was load tested and perfect reading 12.68 V....battery side of solenoid reads 12.68 V...key engaged Voltage drops which is good. Starter side of solenoid read 0 V even with key engaged. Ignition switch has continuity.
New battery cables
New solenoid
New starter
New fuse
It's a four wire solenoid (2 big 2 small). Small white wire only reads 5.5 V
I thought the problem was the solenoid but I've tried 3 of them and the problems remains. Oh yes I can crank the starter directly from the battery. I'm running out of ideas

 

[Mikel1]

5.5 V is not enough. I would first make sure you have 12+VDC to ignition switch(B terminal). If that is good then check the wiring for any damage, make sure grounds are clean and tight. If no problems there then most likely a safety switch problem. The white wire goes from S terminal on ignition switch to clutch/brake then to clutch and then to the solenoid.