Add more codes to be accepted to change the htaccess see BT#12478

plugin/maintenancemode/plugin.php

@@ -157,26 +157,32 @@ RewriteRule \.*$ '.$append.'/maintenance.html [R=302,L]
         $httpCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);
         curl_close($handle);
 
-        // Looks htaccess contains errors. Restore as it was.
-        if ($httpCode != 200) {
+        $statusOkList = [
+            200,
+            301,
+            302,
+        ];
+
+        if (in_array($httpCode, $statusOkList)) {
+            $result = file_put_contents($maintenanceHtml, $content);
+            if ($result === false) {
                 Display::addFlash(
                     Display::return_message(
-                    'Check your htaccess instructions. The original file was restored.',
+                        sprintf($plugin->get_lang('MaintenanceFileNotPresent'), $maintenanceHtml),
                         'warning'
                     )
                 );
-            $originalContent = str_replace("\x0D", '', $originalContent);
-            file_put_contents($file, $originalContent);
+            }
         } else {
-            $result = file_put_contents($maintenanceHtml, $content);
-            if ($result === false) {
+            // Looks htaccess contains errors. Restore as it was.
             Display::addFlash(
                 Display::return_message(
-                        sprintf($plugin->get_lang('MaintenanceFileNotPresent'), $maintenanceHtml),
+                    'Check your htaccess instructions. The original file was restored.',
                     'warning'
                 )
             );
-            }
+            $originalContent = str_replace("\x0D", '', $originalContent);
+            file_put_contents($file, $originalContent);
         }
 
         if ($active == false) {