First, Isolate the wire on the starter that is on the "S" terminal on the solenoid, (closest to the block)
Set your DVOM for DCV, V X 50 or Auto range, put the red probe on the wire, and the black probe to a good ground, have someone turn the key to "Start"..The meter SHOULD read 12 volts.
If not, back track the wire to the Neutral Safety Switch, and do the test again, If it has 12 volts on one side but not the other, Check the adjustment of the switch, If that is good, replace the switch.. (could be on the column or at the transgression<---Misspell..But I like it so it stays..) If you have NO power to the switch...
Backtrack that to the plug at the column and isolate that wire, and measure again..If you have power on one side of the plug but not the other, check the pins and / or wires for dirty, burned or bent pins, clean and burnish the plug anyway..If you have no power on both sides of the harness plug, ...
Remove or gain access to the Switch, and isolate the "S" wire there..measure again, if no power..THEN isolate the "Hot at All Times " wire at the switch..If it has power, replace the switch..If not..
Backtrack that wire to the Solenoid "Battery" cable bolt and fuse link..check both to be sure both are hooked up and not open.
Refer to your own Drawing above..