WebIDE: No iOS device found

Trying to connect to an Iphone using WebIDE on Firefox 39.0 OS X. Get this result. Connecting with Safari works.

“Operation failed: Connecting to Safari, Firefox, and other WebViews on iOS: Error: No iOS device found” webide.js:346:5
UI.reportError() webide.js:346
UI.busyUntil/<() webide.js:327
Handler.prototype.process() Promise-backend.js:870
this.PromiseWalker.walkerLoop() Promise-backend.js:746
this.PromiseWalker.scheduleWalkerLoop/<() Promise-backend.js:688

Error: No iOS device found
Stack trace:
iOSProxy.start<@resource://gre/modules/commonjs/toolkit/loader.js -> resource://fxdevtools-adapters-at-mozilla-dot-org/lib/util/ios-proxy.js:100:13
TaskImpl_run@resource://gre/modules/Task.jsm:314:40
Handler.prototype.process@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:867:23
this.PromiseWalker.walkerLoop@resourc

That question doesn’t fit anywhere in this forum, so I suspect you won’t find any help here. I recommend that you ask in the #devtools channel on IRC.