Does Runbox work with CalDAV/CardDAV in GNOME Online Accounts?

Hello,
I am trying to set up CalDAV/CardDAV in GNOME settings (under “Online Accounts”) on my computer running Fedora Linux 42. When I enter my information and hit Sign In, it just hangs forever. Has anyone else been able to make this work?

(The window in question looks like this: https://www.heise.de/imgs/18/4/5/5/9/9/7/5/02_gnome46_webdav-73fa7a536673bdb3.png)

I am entering the following information:
Server address: https://dav.runbox.com/
Username: (username)@runbox.com
Password: (app specific password)
Files: (blank)
Calendar (CalDAV): https://dav.runbox.com/calendars/(number)
Contacts (CardDAV): https://dav.runbox.com:443/addressbooks/(number)

I am pretty sure I have set up CalDAV/CardDAV properly on the Runbox side, because I have been able to make it work successfully on my iPhone, and in Thunderbird.

I have read every Runbox help page on CalDAV/CardDAV that I have been able to find, so I’m not sure what I am doing wrong. Maybe the functionality in GNOME is broken?

Grateful for any help! :pray:

Working just fine with Fedora 42 on my laptop
Maybe your calendars have a lot of entries and it takes a long time to sync?