I wan’t to set up my calendar and contacts sync at iOS and I have encountered a problem.
When setting up I get an SSL-error. My accountdata are ok and with another iOS-device it works fine. When I changed the network from WiFi to mobile it works.
Apple check the ports 443 for and 8443 and my Router (fritzbox) seems to block it.
On the website you can find more infos: http://sabre.io/dav/service-discovery/
Maybe it would be good to mention this on https://docs.nextcloud.com/server/9/admin_manual/issues/general_troubleshooting.html#troubleshooting-contacts-calendar