I regularly need to connect between myself and another spark user, both of us are in the Wellington region and both are on fibre.


Usually I would connect to this other user via a ddns address, and can usually do so without a problem. 


Recently I have been unable to connect via ddns or but can fine via ip address. I have tried it from multiple devices from within my network.


As soon as I turn on my vpn I can connect to them again via the ddns route, and their ip address. 


They have paid ddns hosting so expiry is not an issue.


Any ideas why this might be happening?