With the recent WordPress 5.5, the jQuery Migrate script has been removed from WordPress, and therefore some functions are not or no longer supported.

Specifically, the affected areas of Uncode that may have problems are:

• Backend Editor
• Theme Options
• Page Options
• Font Utils
• WooCommerce Mini-Cart

Update the Theme and clear cache to fix

To solve possible issues, please update Uncode, the required plugins (Uncode Core), and clear the browser cache, the server cache, and possible extra services (like Cloudflare, Amazon, etc). Here some useful link:

• Theme Update
• How to Backup
• Change Log

Please note that the Uncode compatible update was published on 10th August 2020, about ten days before the official release of WordPress 5.5, so Uncode users can install the update and avoid any issue (like the Backend Button disappeared).

Of course, this is valid for Uncode and for the plugins that are part of the package. If you use extra plugins that are not up to date (or whose compatibility update has not been issued), these could create issues and lead to problems such as Backend Button.

The Enable jQuery Migrate Helper plugin workaround

If, even after the Theme and Plugins update, the problem has not been fixed, this means that you have not cleared all caches completely (especially the server cache caused issues for some users).
As a workaround, you can install, until you are sure you have cleared your cache, a plugin called Enable jQuery Migrate Helper that restores the script removed from WordPress 5.5 version:

• Enable jQuery Migrate Helper