We have noticed a handful of clients reporting issues with their Wordpress websites after updating to version 5.5.

After a bit of digging we have found that Wordpress have removed a javascript function called "jQuery Migrate" that appears to have been used in quite a lot of older themes of plugins, so when users update to Wordpress 5.5 these old plugins and/or themes no longer work.

You can find more information on this, and potential ways to fix things over at the following site:

https://www.searchenginejournal.com/wordpress-5-5-issues/377851/