"After I updated from Thunderbird 52.9 to 60 enlightenment stopped working with all caldav calendars on my nextcloud-instance. It doesn't synchronize anymore and doesn't even show that it doesn't. This is a known-issue, it's a NextCloud problem. There is a workaround:
- Go to the config editor (Settings -> Advanced -> General -> Config Editor)
- Search for network.cookie.same-site.enabled
- Set it to false
For your own security you should set it back to true once this issue is resolved.(Source, accessed 01/21/2019)"