I had a similar question few months back and support has provided the below steps for changing the HUB IP
1. backup hub and robot folders on the remote hub
2. stop the remote hub
3. change the IP
4. delete the file(s) "$nimsoft/hub/security.*"
5. restart the remote hub
6. do NOT login to the remote hub until you see that securty.cfg has been updated (hint: size will increase beyond 1K)
Be aware that robots attached to the remote hub will not know that the IP has changed. It can be helpful to have a temporary hub in place. You move all the robots to the temporary hub by selecting all the robots under the remote hub -> right-click -> Move... in Infrastructure Manager, and change ip address of the remote hub, then move the robots back to the remote hub. Alternately, you can simply edit the robot.cfg for each robot and input the new IP for the "hubip=" field.
Also, defined tunnels will be affected if the remote hub changes IP-address. You may need to recreate the tunnel connection accordingly.
NOTE : Verify the steps again with Support before you try, recommended to test in a UAT/DEV environment before you test it on prod