There are several things chained together in your setup and I would recommend you test each part of the link to find out where the problem sits:
- Check out the voltage between trigger input and hot shoe ground for each flash that you ever tried with your radio triggers. If the voltage of any of your flashes is beyond 10V, you have likely fried your trigger receiver(s). Get new receivers and never connect that flash to radio triggers ever again.
- Set your meter to current measurement (10A range if possible) and connect the test strips to trigger pin and hot shoe ground. If the flash doesn't fire, you can't trigger it this way, don't use it with radio triggers. I have heard of flashes that only trigger with the clock/data protocol used by the specific camera brand.
- I assume that the trigger output of the radio trigger won't stay on very long, so a resistance measurement may or may not show that the output went active. If you use acoustical continuity measurement, you should get an audible beep when the output goes active. This works with my RF-602.
- Now you know that your flash won't fry the receiver, that it responds to a short circuit between trigger input and hot shoe ground, and that the radio link works. Now connect flash and receiver and try the test button. The flash should fire now. If it doesn't: compare flash hot shoe and receiver hot shoe for possible mismatch.
- Leave flash and receiver connected, and use your meter to create a short circuit between trigger input on the radio transmitter and its hot shoe ground. If the flash doesn't fire, something in your transmitter is broken.
- Set your multimeter to acoustic continuity measurement again and check whether the camera actually actuates its hot shoe trigger output.
- If the flash fires when manually shorting the transmitter's trigger input but not when the camera fires, there might be a mismatch between camera hot shoe and radio transmitter hot shoe. I know for instance that I can slide my transmitter onto my RZ67 hot shoe both ways, but only one way will trigger the flash.