Run local Shoutcast station through VPN, is this possible?

[SoLoRiZe]

Hi,

I am trying to run my locally hosted Shoutcast station through a VPN connection
but am having problems accessing the streams.

F.Y.I
If I don't have the VPN running, I can connect fine and the stream plays.
But as soon as I have the VPN run it wont connect.

Setup:
I have the Shoutcast DNAS running, being feed audio from source.
NO-IP running as my Dynamic DNS service. (updating my External IP address)
Router firewall has required ports open to let listeners connect to the stream.

// Up to here stream can be connected to and works fine. //

But.

If I then run my VPN (NordVPN), which then changes my External IP address.
NO-IP then picks up the change in IP Address and displays this in it's interface
(which is what I would expect).
But my stream url now does not let me connect, and therefore does not play the stream.

Does anyone know why this is? and what I need to do to get it to work through the VPN?

I would have thought that even if the External IP address is now change to the VPN's
assigned External IP address, that NO-IP would update to this new IP address and then still let listeners connect through to my streams?

Thanks in advance.