Secure WebDAV, also referred to as WebDAVS or WebDAV over SSL, is occasionally blocked by firewalls, and often firewall changes can introduce new blocks that didn't previously exist.

Files.com does not support or allow insecure plain WebDAV.

The approach should be to find a set of settings that will work for a particular network/firewall. This may vary across your user base depending on what corporate or network firewalls they find themselves behind.

Manually Whitelisted IP Addresses

Have you manually whitelisted any IP addresses anywhere? If so, verify that all of the appropriate IPs are whitelisted, not just some of them.

If your site uses a custom domain, you have two dedicated IPs that need to be whitelisted in your firewall. You can find your dedicated IPs on the Firewall page of your site. If you have a custom domain, you also need to ensure that you are connecting to it, and not to [your_subdomain].files.com.

If you do not have a custom domain, ensure that our main IPs on this list are whitelisted, not just some of them. There are quite a lot of IPs on that list (over 80 at last count) and you need to whitelist all IPs or else you will experience failures. If whitelisting that many IP addresses is a problem for you, the solution is to move to a custom domain. This will get you a pair of IP addresses you can whitelist.

Consider An IP Whitelist

If you have not whitelisted IP addresses, maybe your firewall administrator requires this for WebDAV traffic. Please submit a request to your network or firewall administrator to allow WebDAV port 443 traffic to all of the IPs on this list.