Reported by a user, apparently the library used to fetch the ical file does not support IPv6 out of the box, maybe needs some additional options. Alternative is to force IPv4.
2019-03-12 19:46:11.679 D/SYNC: Syncing event iCal from https://www.facebook.com/events/ical/upcoming/?uid=hidden&key=hidden&locale=nl_BE
2019-03-12 19:46:21.820 E/SYNC: Error retrieving iCal file: 0, Unknown error
2019-03-12 19:46:21.820 E/SYNC: URI: https://www.facebook.com/events/ical/upcoming/?uid=hidden&key=hidden&locale=nl_BE
2019-03-12 19:46:21.820 E/SYNC: Throwable: java.net.SocketTimeoutException: failed to connect to www.facebook.com/2a03:2880:f121:83:face:b00c:0:25de (port 443) from /[hidden] (port [hidden]) after 10000ms
Reported by a user, apparently the library used to fetch the ical file does not support IPv6 out of the box, maybe needs some additional options. Alternative is to force IPv4.