Enabling:
define('WPSEO_CSSJS_SUFFIX', '');
define('YOAST_ENVIRONMENT', 'development');
is not helping on understand what is happening, seems that file is compiled.
As I can see is missing the i18n library and is loading the polyfill from the amp plugin but what amp offer seems incomplete.
Those are the line with errors https://i.imgur.com/yoUTaja.png
I replaced the content of i18n.js (from the latest wp release) in the AMP plugin and now yoast is working without issues.
Hi,
We see you are having some JavaScript errors that appear to be preventing the Yoast Metabox from loading.
Can you confirm all your non-Yoast plugins and themes are updated?
If so, please Check for conflicts.
If you find any JavaScript errors related to Yoast SEO or if there is a conflict with a plugin or a theme, you can create a new GitHub issue for our developers. Please report the issue to a third party developer as well.
If you didn’t find any conflicts or errors, we think the issue is specific to your site. We’d need to investigate further but are unable to do so on these forums. You can purchase Yoast SEO Premium and receive our Premium email support and we can help you further.
Recently I swtiched to the 7.3 latest Stable PHP version on my server. Today I tried to go back to PHP 7.2 — yoast meta box is visible again 🙂 Yoast is not compatible with 7.3 php
It isn’t a PHP issues but a browser one. This plugin is loading a polyfill from AMP plugin that is not a complete polyfill for WP 4.9.
