https://www.amazon.com/gp/product/B0B3987YZD/

To be exact, the h5a is the one that you can put on a mount(essentially a big POE 2M tripod mountable camera), we have the mic mounted to the top.

That's more likely to short out on the other signal outputs.  What kind of mic are you using?

So something like this to convert it down might work?

https://www.amazon.com/dp/B08V53BJ54/

Your microphone may have the wrong pinout to use with their port.

It also only accepts line level mono audio.

Manual here: https://www.avigilon.com/support/cameras-sensors/h5a/avigilon-h5a-dome-camera-installation-guide-en.pdf

I've plugged a standard 3.5mm microphone into the camera but I only get buzz/static, tested the mic on a PC, works great. Thoughts?

2.0C-H5A-B2 microphone port