WordPress 5.5+ caused issues for a lot of plugins as it removed the jQuery Mirate script from the site which a lot of plugins appear to have been relying on.
If you open up Chrome Dev Tools when testing the above and look in the ‘Console’ section, do you see any errors?
That will point out which plugin is throwing the error.
Or, what you can do is install and activate this plugin:
Which adds the migrate script back onto the site, but will also add a notice every time it is used as the intention is to get your site back up and running whilst giving you time to contact the developer of the theme/plugin and fix the code.