I recently updated to Firefox 56.0. I was using uBlock Origin before the update, and it worked fine, but after updating the addon disappeared from the addons area and didn't function, and a reinstall didn't help. I did some digging and it looks like the latest version of the addon that works is 1.13.8, the last version without WebExt. I tried installing the addon both in FF Safe Mode and in a different Windows profile with a refreshed FF. Installing in Safe Mode didn't work, same problem. But installing with the refreshed FF worked fine, even though I was using the same uBO and FF versions. I looked at the browser logs when I installed the addon both times, here's the log for the refreshed FF: https://pastebin.com/hNDcrY97 and the one for my normal FF: https://pastebin.com/h0CFTPZD It looks like the problem is "Error: Out-of-process WebExtensions are not supported with multiple child processes." I did discuss this with the head developer, but they couldn't recreate it on their end so there's not much they can do. In about:config, "extensions.webextensions.remote" is set to true. I'd like to only refresh my FF profile as a last resort, since I have a lot of addons/other custom settings that would be a pain to restore. Is there anything else I can try to track down the cause/solution to the error? Thanks for your help!