Plex works on Mobile but not on Desktop

Hi,

I've shared my Plex server so I can access it remotely. It works fine on 3G and Wifi (that is not my own Wifi) but on the desktop/web app, it doesn't see to work. I'm using the same wifi and it will play fine on the iOS app but again, not on the web app.

I've tried on multiple different Wifi's and it's the same. Works on mobile but says unavailable on the web app.
Is there a setting I'm missing here?

Thanks for the help.

Adrian