Hi @Larry_C-84
Thanks for posting in our business forum.
Here's the explanation of the Port Isolation feature from the User Guide:
Click the checkbox to enable Port Isolation. An isolated port cannot communicate directly with any other isolated ports, while the isolated port can send and receive traffic to non-isolated ports.
If you don't know any terms in the Controller, please refer to the User Guide or click the icon for Help Center.

So, your goal is to isolate them, my first question would be is this a wireless network? You have EAP? If your answer is yes, then you can set Guest Network. The isolation happens naturally.
If they are wired, unlike the standalone mode, where you have a feature called "port security". In there, you can literally enable port isolation which allows/blocks the traffic.
If this is entirely based on wire connection, then there is no way to block it. You can refer to what MR.S said. But it still fails to achieve what you want.