Try adding esr firefox version
Try adding esr firefox version

It's the extended support version which is 45 and hopefully still works with webdriver. I noticed that that's what the adapter.js tests use
https://travis-ci.org/webrtc/adapter

opentok/opentok-meet,opentok/opentok-meet,aullman/opentok-meet,aullman/opentok-meet,opentok/opentok-meet