
when i log in to youtube, i can't view videos in full screen. but when i log in using other id, full screen works.
happened recently on Firefox Quantum on MacBook Pro using MacOS Mojave.
1) login youtube using 1st ID, youtube cannot play in full screen. 2) login youtube using 2nd ID, youtube can play in full screen. 3) login youtube back using 1st ID, youtube still cannot play in full screen. 4) did a full refresh multiple times, but still the same outcome. 5) firefox sync had been disabled (initially enabled) but still the same outcome. 6) tried to look for "settings" based on logged in user id, but can't seem to find it. 7) Tried using google chrome, no problems for full screen view using 1st ID.
please help as i love to use firefox for browsing.