Before changing port number, you need to make sure to add this new port number to your firewall list to recognize. Otherwise you wont be able to use this new port number.
Now that you have changed the port number and the firewall doesnt know about this new port number, you wont be able to access the site using new port number.
What you can do now is stop firewall and then access cyberpanel, and add this new port number in firewall.