I am trying to power on the transmitter, but for some reason it doesn't work. The PA system is on and working and I have new batteries in and they are correctly placed, but it still doesn't work.

The 9V battery is for the mic or the transmitter from what I can tell. According to the manual, the bottom of the mic is where the battery compartment is located, and it unscrews. You can get the manual here: http://www.pyleaudio.com/sku/PWMA200/Rechargeable-Portable-PA-System-with-Wireless-LavalierHeadset-MIC-and-1-Wired-Mic

Put it in MONO mode.
You can also make a cable where the TIP and RING are wired together....

Have you checked the cables? If that doesn't fix it, you probably have a loose connection inside between the "mixer" unit and "amp" unit

Make sure the battery is placed underneath the small copper clip (positive lead) inside, else the circuit isn't complete. It's pretty easy to clothes the battery casing with it above the lead and not even notice it.

Sounds like the cells inside of the battery went bad. Try another known good working battery, if the red X goes away on the battery then you know the original battery is bad. If the red x stays on the new battery then that means either your power adapter is bad, which you can try replacing that as well because it might not be putting out the correct voltages to charge the battery. If that doesn't work then the motherboard is bad for sure.

You need power from the transmitter to power this mic. See your mics specs to determine if it needs "Phantom Power"
Perhaps the transmitter doesn't supply power. Condenser mics may not work. Stay with the dynamic type. IMHO

Resynchronization may be necessary due to the security method used by the remote keyless entry system. The transmitter does not send the same signal twice to the passenger door module (PDM). • The PDM will not respond to a signal that has been sent previously. This prevents anyone from recording and playing back the signal from the transmitter. • The panic button should still operate normally when the system is out of synchronization. • Resynchronization may be necessary under the following conditions: - The battery in the transmitter is very weak. - The battery in the transmitter was replaced. - The battery in the vehicle has been in a low or no charge condition for an extended period of time. • In order to resynchronize the transmitter with the PDM, perform the following steps: 1. Stand within 1.5 meters (5 ft) from the vehicle. 2. Simultaneously press and hold the LOCK and UNLOCK buttons on the transmitter for 7 seconds. The door locks should cycle in order to confirm resynchronization.

it comes with a transmitter. so put batteries in the transmitter and plug the included (white) audio plug in the back of the transmitter, (the hole that says direct input), turn transmitter on. Plug free end of audio cord into headphones jack on ur computer. put batteries in the speaker or plug it in to wall and push power button. push reset button on front of speaker and it should work. start playing music

Try to download the Operating System from http://www.korgpa.com/pa_root/en/products/pa50.html?en

You need new SioScan Temperature Transmitter 433 MHz. Take a look on amazon La Crosse Technology TX6U Wireless Temperature Sensor for 433 MHz units.... Hope this was helpful. cheers