arnaudS-4

Problem:
Learndash courses disappeared from the frontend after updating to WordPress 5.8

Solution:
The debug log file showed the following error:

PHP Fatal error:  Uncaught InvalidArgumentException: element_id and type do not match for element_id:42 the database contains post_attachment while this function was called with post_post in xxxx/wp-content/plugins/sitepress-multilingual-cms/classes/core-abstract-classes/class-wpml-set-language.php:34

And it was fixed with the following steps:

Go to WPML > Support > Troubleshooting page, then click these options:

- Clear the Cache in WPML
- Remove ghost entries from the translation tables
- Fix element_type collation
- Fix WPML table collation
- Set language information