POL Won't Load On Certain Wifi Connections

Interesting issue I've encountered. I usually use a VPN for my pc. This particular instance turned it off and booted up FFXI at work on their public wifi. I get an error message when trying to log into POL (saying network connection issue, please try again). When I turn on my VPN, it boots right up.

Is there a port or something that my workplace has turned off that FFXI accesses? I just thought it was weird. Any ideas?

They quite possibly have many ports blocked, it is often used to have stable public wifi, some of the settings are legacy from old ways of thinking too.

If you have a VPN already just use it.