Hi Ed,
What version of Chrome is GapDebug configured to use?
The reason for asking is we have a fix in the pipeline for an issue that appears in Chrome v48. The Chrome dev team made a major change in v48 that causes the iOS debugger to fail to load. You can quickly determine if you being impacted by this issue by opening the chrome dev tools on the GapDebug UI (right-click Inspect). If you see an error in the console for getCSSCanvasContext() undefined then you hit the issue.
If the Chrome bug is impacting you there are 2 options:
1) wait until Thursday when we roll out the update
or
2) install the beta of the GapDebug update that includes the fix https://www.genuitec.com/forums/topic/beta-1-of-gapdebug-2015-update-6-available-please-give-it-a-go/
And if you are not affected by that issue then the most common reason for an iOS app not being detected by GapDebug is building the app with an ad-hoc provision profile rather than a developer profile. But you indicated you are using a developer cert/profile pair.