Hello, I've been using Lightning 5.4.1 on Thunderbird 52 to sync my ownCloud CalDAV calendars for a long time. But recently I've upgraded my ownCloud server to version 10.0, and a bizarre thing happened. All of my ownCloud calendars have been "unchecked" in the calendars list, and clicking on the checkboxes does not check them. So I right clicked on my calendars, selected "Properties", and in the resulting window checked the "Switch this calendar on" box. The strange thing is that my calendar would be switched on for about a second, then suddenly disable itself again. This is a big show stopper for me as I can't function without my calendars! How do I troubleshoot this problem? Thanks!