Hey,

Regardless which NTP server I choose I get the same error message.
NTP server not responding
About my system see attached files

A couple of things you can try:

Enable Automatic DHCP

Reboot your ISY

@dpichow what kind of router are you running and are you running any hardware firewalls or high firewalls rules on your router? 

Have you changed your router recently?

It seems that something could be blocking the traffic from the ISY994 to the external NTP. 

Otherwise, your running an outdated firmware (5.3.0 released 2020). First step would be to bring it up to the last release that works for your ISY994 system (since you are at 5.3.0 you would go to 5.3.4 (released 2021). That is a very simple update (at least it seemed to be back when it was released).