I have only done it the one time, and it was a full server reboot.
It is not in production currently. Did you want me to try and restart the gluu service?
Upon reboot, the Gluu service started, no problem. And inside the Gluu container, a 'service --status-all' showed idp as up, but the 503 error was happening. Restarting the idp service fixed that, as it did the first time, pre-reboot.