I'm trying to learn what is preventing my install of Firefox from using multi-process functionality (also called "Electrolysis" or "e10s"). Mozilla's wiki gives instructions on how to force enable multi-process windows and I have already changed
browser.tabs.remote.force-enable to 'true'.
Checking about:support I see the message "Multiprocess Windows 0/1 (Disabled by add-ons)"
However this message persists even after restarting Firefox with all add-ons disabled. I have taken the additional step of checking arewee10syet.com and if the data on that site is correct, all my extensions are compatible already.
How can I troubleshoot this further, and discover what is preventing me from enabling this feature?