I have just deployed Firefox 59.0.2 for a customer on multiple shared servers (150+ users). We used to use CCK2 but as its no longer supported we need to move over to AutoConfig. I have followed the guide here exactly: https://developer.mozilla.org/en-US/Firefox/Enterprise_deployment_before_60 I always get an error "Failed to read the configuration file. Please contact your system administrator." As specified in the above guide, I create an autoconfig.js file and enter the following information (copy/paste from guide). // Any comment. You must start the file with a single-line comment! pref("general.config.filename", "mozilla.cfg"); pref("general.config.obscure_value", 0); I then create a mozilla.cfg file and enter the following information (copy/paste from guide) // Any comment. You must start the file with a comment! // Disable updater lockPref("app.update.enabled", false); I have tried this on Windows 10 and Server 2012 R2 with the same version 59.0.2 with the same result. I have also tried adding these 2 files into both defaults/pref and browser/defaults/preferences with no difference. I am at a loss at this point. Any help would be appreciated.