If this happens, you can see by the 503 error that something on your site has crashed. Please check the woo logs first in WooCommerce/Status/Logs; in particular the woo-vipps and fatal-error logs (you will need to match the date and time with the error).
If there is nothing in the fatal-error log, you will need to check your system error logs; first the PHP error log, and if you cannot locate any fatal errors there, the web server log (the 503 should be logged as an error there too, if the cause of it wasn’t in WordPress but in the web server).
Hopefully you’ll find the fatal errors in the WooCommerce logs. You will then need to find what system or plugin caused the error, which will often be apparent by the backtrace added to these logs. If the error is in the Vipps plugin, we’d appreciate a bug report either here, or if there logs contain anything sensitive, directly to us.
