Heater/AC stopped working

This would point to an issue that is shorting the module when you turn the key on.

So I just want to make sure we are on the same page.

When you turn the key and power it up the first time after replacement, it works properly? Then when you cycle the key again it stops working?

If this is the case, we need to unhook the connector and find out what the voltage is on the two power wires and the ground.

https://www.2carpros.com/articles/how-to-check-wiring

Basically we more than likely have an issue on the ignition feed wire which is labeled in the diagram. If this corresponds with a key cycle then monitoring that voltage when you turn the key on would be interesting to see. Maybe we are getting a voltage spike.

Otherwise, where are you getting these modules from? Are they used/salvage yard or are they from a company?

If they are from a company I assume they are warrantying exchanging them? If so, can you contact them and ask that they bench test it to find out what circuit is failing to cause it to not come on? This will tell us if there is another circuit that is causing the issue.

Lastly, we can't rule out just a bad product. This is not common but it does happen.

Let us know what you find with all this info and we can go from there.

Thanks