Can't connect iPhone 15 to MacBook

It should appear in the "Locations" section in the Finder side bar.

Make sure Locations is expanded there to see the iPhone.

Also, make sure the cable being used is rated for data transfer, and not only for power transfer (charging).

The iPhone should request you trust the computer when it detects it.

Its probably collapsed or beyond the visible area.

If you can see the "Locations" label but there is nothing under it, then click on the > next to the label to expand it.

If you see no Locations label at all, try scrolling up on the sidebar to reveal more options.

If it's still not there, go to the Finder Menu ➜ Settings ➜ Sidebar, and make sure at least one option is selected for "Locations". Specifically the CDs,DVDs and iOS devices option to show the iPhone.

Glad it worked out.