Problem: If you're experiencing the error "Updating failed. The response is not a valid JSON response." when updating alternative language content in WPML, and you've already tried disabling all plugins, switching to the default theme, increasing the memory limit, and clearing the cache without success, the issue might be related to server redirects, database inconsistencies, or PHP version compatibility.
Solution: First, ensure there are no redirects set up by a plugin, .htaccess rule, or directly within the server that could be causing the issue.
Additionally, check your PHP version. WP/WPML may not be fully compatible with PHP v.8.3, so we recommend downgrading to a more stable version like PHP v.8.1 or v.8.2. After adjusting the PHP version, re-save your permalinks under WP-Admin -> Settings -> Permalinks and see if the issue persists.
If the solution provided here does not resolve your issue or seems irrelevant due to being outdated or not applicable to your case, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If necessary, please open a new support ticket for further assistance at the WPML support forum.
