I am on Ubuntu 18.04, and I added my Nextcloud account (version 13, I pay a provider) via the "settings -> online accounts" menu. The NextCloud account seems to be recognised: if I open the Calendar app (version 3.28.2) and click on the "manage your calendars" icon, they are listed in there and ticked (see picture).
However, the grid does not show any events, and the top panel's drop down calendar neither.
I have logged out and back in, and restarted already.
Any idea what the issue might be?