At this point, the transmitter should work again. Let's check it out and take the multimeter.

Set it to 2000mV and add the measuring pens on the sensor contacts. It should show 019.

If yes ... congratulations! You can move on to the next step.

If not, there's a contact problem. First, check the upper contact plates. Set the multimeter to continuity.

Touch one pen on the plate and the other on the battery. 000 should be displayed.

If not, you have found the problem. You have to remove it, clean it, and re-glue it.

If both plates have continuity, you have to check out the lower contacts and remove the batteries again. Maybe pull up the lower contact a little bit before attaching the battery.