Bring up the Asterisk console (asterisk -r from your terminal) and set verbose (CLI> core set verbose 9). Then try to place a call with webrtc. See whether it tries, and whether any errors appear in the console.
Also try bringing up the Javascript developer console in your browser (in Chrome, it’s View - Developer - Javascript Console). You will see informational messages there as you attempt to place a call. Mine looks like this:
