First, check that you entered the right IP in the ax command. If you still cannot connect, the output of ax nodes ls returns one of the two possible reasons (if you are using the ActyxOS Node Manager, you can find this info in the Status tab):
ActyxOS is not reachable: This means that ActyxOS is not running on your node. Please start ActyxOS described in this guide.
Host is not reachable: This means that your development machine cannot connect to your node. Please check that your development machine and your node are in the same network, and your firewall(s) allows them to connect via port
4457. You can debug the connection as explained in this guide.