WebDAV access denied

Running Linux Mint 20.3. When I try to access Icedrive with Nemo or other apps (two other network backup programs), I always get: HTTP Error: Could not connect: Permission denied.

I have set up the the WebDAV access settings in my Icedrive account. I am very carefull to use the URL and access key given there. What is wrong?

Screenshot from 2022-12-22 20-17-14

Update: WebDAV Server Update