Can not sync with Nextcloud calendar

[Schievel1]

In my config.el I put

(require 'calfw)
(require 'calfw-ical)
(setq calendar-week-start-day 1)

(defun my-open-calendar ()
  (interactive)
  (cfw:open-calendar-buffer
   :contents-sources
   (list
    (cfw:ical-create-source "personal" "https://myURL/remote.php/dav/calendars/myUsername/personal" "Purple")
   )))

So, when I open that URL in a browser, I get a page that says This is the WebDAV interface. It can only be accessed by WebDAV clients such as the Nextcloud desktop sync client.. So I think the URL is correct.
When I run M-x my-open-calendar in emacs, it is asking for my username and password for nextcloud, it then displays [(==) iCal:personal] at the bottom, but it does not show any appointments.
If i press r it shows Contacting myURL:443 but nothing more.
If I mangle that url a bit, like changing my username or the calendar name personal, it does the very same, that's the reason why I think sync is not working.

[tim3trick]

I had the same problem, in fact the URL seems incorrect, I got mine to work with the export URL (which is just /?export attached to what you currently have.)