Hi my name isXXXXX to just answer.
This problem can be very frustrating to get undone. The purpose for the second latch is for when the cable breaks it won't let the tire fall off. Unfortunately, the latch rusts and will not operate properly.
You have to hold up the tire with another jack on both sides to take the pressure off the cable.
let about 6" of cable out and at the bottom of the latch you will see a sleeve. working the sleeve up into the latch and moving the latch up and down should release it. Use lots of WD 40 to lube the latch. It is not an easy task, allot of the times we have to cut the cable and replace the hoist, if it to rusted to get released.
Here is the instructions from the service manual.
The key is to get the sleeve to move up,this is what releases the latch.
Tire Hoist Secondary Latch Mechanism
Important: If the spare tire hoist has been fully raised without a spare tire in place, the secondary latch mechanism may have become engaged. If this has occurred the hoist will not lower and the following steps will need to be followed:
I sorry the link did not show, The weight of the tire is what is suppose to push up on the button in the latch. When it gets rusted it cant move it to release it. Spray it down good to loosen it up, and tap with a screw driver and hammer on the center bushing.
I will try to send the info again a different way.