Can you check the values of the preferences mentioned in this documentation: https://firefox-source-docs.mozilla.org/remote/cdp/RequiredPreferences.html ? It feels like you might be affected by process changes related to Fission?
Bug 1774476 Comment 11 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Can you check the values of the preferences mentioned in this documentation: https://firefox-source-docs.mozilla.org/remote/cdp/RequiredPreferences.html ? It feels like you might be affected by process changes related to Fission? Edit: Just saw that you attached a log and the error message we normally display for invalid preferences is not visible there, so maybe not related. Still worth checking.