Magento shows Error 503: Service Temporarily Unavailable page will appear after extension installation via Magento Connect or taking scheduling a backup in magento store.
-
If you see the page in your site like UNCHECK IF UNSURE , then Magento was switched into Maintenance mode, by maintenance.flag file in root directory.
-
Put store on the maintenance mode while installing/upgrading checkbox was enabled during extension installation in Magento Connect Manager.
-
When this option is checked while installing/upgrading, maintenance.flag file will be created in the root directory in your cPanel and which makes Magento site switched to the Maintenance mode.
-
Another possibility to occur this issue by taking scheduling new backup. Maintenance mode was to enable Put store on the maintenance mode while backup creation option. So do check and uncheck this option while taking schedule backup or installing/upgrading in Magento.
-
To turn the maintenance mode off you need to delete the maintenance.flag in your root directory via FTP or File Manager.