Hey Trevor,
if you mention the “onefinity.local” URL I think you followed the text and video in
How to directly connect your Onefinity CNC to a computer/laptop (no screen present). Did you turn WiFi off on your Mac before trying? The reason is explained here.
But the most simple thing you can do is: On your Onefinity Controller display, there is an IP address shown, in the form “xx.xx.xx.xx” (“xx” being decimal numbers from 0 to 255). Open a web browser on your Mac, enter this IP address into the address bar, and voilà, you’re done.
If it does not work, there could be a number of reasons but problems can be solved. Many people use a remote computer to control the Onefinity, which has the advantage that you can see the camotics toolpath simulation which unfortunately the Raspberry Pi inside the Onefinity does not show on its display.