The tip and the long sleeve should give zero resistance when testing it with an ohm meter - when the button is pushed . . .
Zero resistance.
The plug has 2 black bands....that means it is a stereo jack...could that be a problem?
If it shows zero resistance only when the button is pushed; then it is working correctly.
You probably don't have the mic cable wired properly. But you do have an ohmmeter. Time to start learning how to do it now. If you can't do this; then take t to a shop that can.
Ok...here is what I got.....Behringer 802 mixer and a mxl v63m mic...I got it hooked up....the ptt works...it keys the radio......but I am getting very little audio.....the mic and mixer are working because I tested them by plugging them into my marshall amp....and they work good..and sound good....I cannot figure out why I am not getting audio when I key up the cb?
Just because the cable keys up the radio, and the mixer/mic works thru a Marshall, doesn't mean the the radio/mixer cable is still wired correctly.
However; you are almost there . . .