Some FTP clients require you to enter your store's servertrust address instead of the domain name or IP address. You may also need to use the servertrust if you haven't pointed your domain name to your store.
To find your servertrust address from your MyVolusion account:
Log in to my.volusion.com.
Click Manage FTP in the left navigation menu under my Stores.
Select your domain from the Choose a Domain menu.
Your servertrust address will be listed under the Temp URL label.
To find your servertrust address in your store's Admin Area:
Go to Settings > Company.
Click the Domain Name menu and find the Temporary Hostname option. Your store's servertrust address is listed next to Temporary Hostname in the following format: xxxxx.xxxxx.servertrust.com