I’m having this same issue, but even after deactivating my Cache plug-in (WP-Optimize), the Hamburger Button still will not work. Along with this, side widgets that had video on them suddenly either showed the video full size (thus sending it off the page and past the widget square), or showed a blank video player. I removed them for now, but the hamburger button is most important.
This all seemed to have happened after WordPress 5.5 for me, so I’m wondering if that’s related. Any idea for a work around? I did note before deactivating WP_Optimize that it did not have Mini-ing turned on.
Thanks for all your help!
Jason
game-rave.com