Download Mozilla's Add-on Compatibility Reporter (https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/) to see which of your add-ons is preventing Firefox from enabling e10s.

That I already did. As I wrote, I removed all plugins the compability reporter told me isn't compatible, yet still tells me that it is deactivated due to plugins. I have both tried deactivating them and I also completely removed them afterwards, but nothing.

Are you running a custom theme by any chance? I've noticed that using a theme will disable e10s for some reason.

Also, try to flip these prefs in about:config

• accessibility.force_disabled -> 1
  • browser.tabs.remote.disabled-for-a11y set to false.

Few more troubleshooting steps in about:config

Go to "about:config" and set browser.tabs.remote.autostart to "false," restart Firefox and check if e10 is enabled Go to "about:config" and set extensions.e10sblocksenabling to "false," restart Firefox and check if e10 is enabled Go to "about:config" and set accessibility.loadedinlastsession to "false," restart Firefox and check if e10 is enabled Go to "about:config," right click accessibility.lastloaddate, and click "reset," restart Firefox and check if e10 is enabled Go to "about:support," and check if mulltiprocess is enabled

extensions.e10sblocksenabling to false did the trick. Thank you. :)