A Fluke 323 is a clamp meter. It's a very odd choice for this kind of work. If you have a Harbor Freight near by, you can get an acceptable meter for under $5.
It would probably be best to get a meter more suited for the task before proceeding, or borrow one from a friend.
With that out of the way, you aren't getting a reading at terminal 12, and that's a problem. There is black wire from terminal 12 to terminal 3, so either a wire is missing or it isn't soldered properly. This most often happens at the headphone jack.
If you are wondering if a wire is well soldered, try pulling it out with pliers. If it's well soldered, it won't come out. If it's not well soldered, it will slide right out of the joint. (note that adding more solder isn't the solution, but rather taking half a wrap around the terminal to make a mechanical connection)
-PB