I have an HF R700 that I have used extensively with a Bluetooth external microphone. The mic has a jack where you can add a lapel mic. Because the Bluetooth one is big and chunky, I ordered a lapel mic to go with it. I connected everything but the camcorder does not get any sound. I removed the lapel mic and went back to the Bluetooth only, and now that doesn't work either. Just to be doing, I plugged the lapel mic straight into the camcorder. No sound that way either.
The only way I can get sound to record now is with the built-in microphone. Is there some setting that has been changed? Could the external equipment have "fried" the jack?
A lot of the lapel mics on the market right now are designed for cell phones and tablets which use a slightly different port configuration and may not be functional with cameras and camcorders, it may be a good idea to check with the manufacturer of the mic in case they can give a little insight to this as well. It is possible the mic can fry a mic port but it is not very common. More often there may be dust or debris in the mic port preventing a solid connection. Take a peak into the mic port with a flashlight and see if there is anything obstructing the contact areas inside.