How to stop multiprocessing being disabled on start?

* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#Summary I am unable to enable multiprocessing. I tried enabling it by setting `browser.tabs.remote.autostart` to `true` in `about:config`. However whenever I quit and re-open the browser, that setting has been changed back to `false`. How can I get it to stay `true`? # Details: * Firefox 64.0.2, 64 bit, Windows 7. * This computer is managed by my employer. However I installed Firefox myself, straight from mozilla.org. * `about:support` says `Multiprocess Windows 0/1 (Disabled)`. (Note that if an add-on is causing multiprocessing to be disabled, it will say "Disabled by Add-on", which is not what I'm seeing.) # What I've tried: * I have disabled my addons. * I have looked for prefs.js and mozilla.cfg in the locations listed here: https://support.mozilla.org/en-US/questions/1237547 The only one which exists is `C:\Program Files\Mozilla Firefox\defaults\pref\pref.js`. I do not have sufficient permissions to modify or delete that. The contents seem unrelated: ``` /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ //pref("app.update.channel", "release"); ``` * I went to `about:support`, clicked on "Profile Folder: Open Folder", (C:\Users\$USERNAME\ApPData\Roaming\Mozilla\Firefox\Profiles\$HEX.default`) searched for prefs.js in that folder. I quit firefox, changed the `browser.tabs.remote.autostart` setting there to true, saved, and started firefox again. The setting in `about:config` was false, and `about:support` shows multiprocessing is disabled. Impact: I am not able to use the "responsive design" functionality. Also, the browser is quite slow. (I don't even have many tabs open, always < 15)