Nextcloud Desktop Client connection error with server

Hi, I have a problem connecting my windows desktop client to my NextCloud installation on my server. When I log in via web browswer everything works fine but when trying to use the windows desktop client I get an error message saying “server not found”. Please view attached screenshot for the full error message. Any advice to solv this problem would be very much appreciated. Thanks

Firewall? Is it https:// instead of http:// ?