Keep in mind all our proxies are located behind load balancer and with a load balancer, therefore connections may appear to come from different IPs to outside services.

The simple solution for this (if you want to only use one IP Address) problem is to connect to the proxy directly, as this will bypass load balancer. 

To connect directly, please use one of the static IPs from your dashboard instead of DNS name of the proxy

If you're using FTP,  if your FTP provider supports SFTP (secure FTP over SSH) then you can use load balanced connections. If not, you'll need to do the above to allow for FTP access.