Restoring config on new hardware Gateway Priority defunct

[Knightmare]

I'm having trouble accessing the Internet when restoring the configuration on to different hardware. I have reconfigured the LAN and WAN on the new interfaces however, when I create a new Single Gateway the priority is labelled defunct
 
Has anyone else experienced this issue when restoring the configuration onto different hardware? It's driving me mad.
 
I've attached a screenshot of the issue