This add-on is still working on my Firefox now(Feb~Dec-2023).
On some version of Firefox, You must maybe settings(Option or "about:config").
Please read more about this add-on page.
After add this Extension, YouTube Videos became not pause. Thanks!

2023/12/2 P.S.
If playlist still pauses, some settings may be incorrect.
First make sure latest version is "0.9.2".
In some version of Firefox, turning on the permission switches of accessing "youtube.com" for may work (Manage Extensions).