[Closed] Internal server error when activating the plugin

Hi,

Thank you for contacting WPML Support. The Internal Server Error issue usually happens due to specific plugins or themes on your site. To address this, could you please follow the below steps and see if this resolves your issue:

1. Please take a backup of your site first for safety reasons.

2. Please add the below code in the functions.php file of your theme:

add_filter('mod_rewrite_rules', 'fix_rewritebase');
function fix_rewritebase($rules){
    $home_root = parse_url(home_url());
    if ( isset( $home_root['path'] ) ) {
        $home_root = trailingslashit($home_root['path']);
    } else {
        $home_root = '/';
    }
  
    $wpml_root = parse_url(get_option('home'));
    if ( isset( $wpml_root['path'] ) ) {
        $wpml_root = trailingslashit($wpml_root['path']);
    } else {
        $wpml_root = '/';
    }
  
    $rules = str_replace("RewriteBase $home_root", "RewriteBase $wpml_root", $rules);
    $rules = str_replace("RewriteRule . $home_root", "RewriteRule . $wpml_root", $rules);
  
    return $rules;
}

3. Please re-save the permalinks from the Settings >> Permalinks page by pressing the Save Changes button.

4. Please delete all sorts of caches on your site/server cache if any / plugin cache / CDN cache, clear the browser cache, and then see if it resolves the issue afterward.

Here you can see more details about it:
https://wpml.org/faq/why-is-htaccess-getting-overwritten-with-the-language-folder-on-my-wpml-website/

Please let me know the results,
Thank you