If you’re experiencing problems after updating to WordPress 5.5 on Siteground web hosting, it’s likely to be an issue with jQuery Migrate which is not included in the latest version of WordPress. This can cause issues and problems with WooCommerce, Wp-Admin and dashboard access, and various plugins. The simple fix is to install the following plugin: Enable jQuery Migrate Helper.
This is the first time we’ve experienced a major problem updating the core of WordPress. This caused us major problems – I’m switching off auto-update on WordPress versions moving forward.