Please move to other forum when not appropriate.

Also note that many of the plugins and the theme will probably not work with current PHP versions. However, you may be able to save the contents of the project along the way.

Merci pour vos réponses

One possible issue could be that if the WordPress installation was initially set up as a multisite network using subdomains, the necessary database tables would have been created specifically for that configuration. Switching to subdirectories by setting SUBDOMAIN_INSTALL to false may cause errors because the required tables for subdirectory-based sites might not be present.

To check if the correct tables exist, look for tables such as wp_site, wp_blogs, and additional site-specific tables like wp_2_posts in your database.

I recommend trying this setup first on a staging server to avoid potential issues on your live site. You can refer to this guide as a reference.

It sounds like a server-side issue, possibly caused by memory limits or PHP configuration. Try the following steps:

1. Increase PHP Memory Limit: Edit the wp-config.php file and add define('WP_MEMORY_LIMIT', '256M');.
2. Check Error Logs: Look at the server’s error log (via cPanel or hosting control panel) to identify specific issues.
3. Disable Plugins/Themes: If you’ve installed any previously, rename the plugins or themes folder to disable them.
4. Verify File Permissions: Ensure folders are set to 755 and files to 644.
5. Check PHP Extensions: Make sure required PHP extensions like mysqli are enabled.

This should help troubleshoot and resolve the 500 error or blank page issue.

1. Backup Your Site: Always back up your WordPress site before making major changes.
2. Edit wp-config.php: Add define('WP_ALLOW_MULTISITE', true); just before the line /* That's all, stop editing! */.
3. Network Setup: Go to Tools > Network Setup, choose “subdirectories,” and follow the instructions to edit your wp-config.php and .htaccess files.
4. Modify .htaccess: WordPress will provide code to add to your .htaccess file to enable the multisite network with subdirectories.
5. Activate Network: Complete the setup and activate the network to start using subdirectories for your multisite setup.

This approach allows you to achieve the desired structure for language navigation without relying on additional plugins.