Your web server is not properly set up to resolve “/.well-known/caldav”. _
Your web server is not properly set up to resolve “/.well-known/carddav”.
add
Redirect 301 /.well-known/carddav https://domain.com/nextcloud/remote.php/dav
Redirect 301 /.well-known/caldav https://domain.com/nextcloud/remote.php/dav
to nextcloud.conf
Alias /nextcloud “/var/www/nextcloud/”
<Directory /var/www/nextcloud/>
Options +FollowSymlinks
AllowOverride All
<IfModule mod_dav.c>
Dav off
</IfModule>
SetEnv HOME /var/www/nextcloud
SetEnv HTTP_HOME /var/www/nextcloud
</Directory>
Redirect 301 /.well-known/carddav https://domain.com/nextcloud/remote.php/dav
Redirect 301 /.well-known/caldav https://domain.com/nextcloud/remote.php/dav