After the upgrade, we had issues upgrading and provisioning phones. The phones were receiving commands from the server, but they weren't downloading the new configs and firmware (they were just restarting) It turns out, they were trying to get the configs using the external IP/FQDN with http instead of https. Since the new webserver that was used has http access from external IPs disabled, everything was failing. Fixed this by editing the config file of the webserver to enable access to http from outsite networks. Then restarted the webserver to apply the change.