Your Mac needs to trust your iPhone or iPad—and vice-versa. Apple added a Trust button to iOS years ago that appears when a device is connected to a computer, requiring a phone or tablet be unlocked and the connection confirmed. This was another layer in attempting to ensure that a device’s owner really wanted that computer to have access.
However, you can run afoul of this provision. My dad wrote to me from a small island on Greece recently after he’d swapped in a Greek carrier’s SIM for his unlocked AT&T iPhone. While voice, text, and data worked fine, whenever he plugged his iPhone into his laptop, he neither received a Trust dialog nor could get his phone’s images to appear as available with iTunes, Photos, or Image Capture.
Apple suggests that for a trust problem, you perform a focused reset via Settings General Reset Reset Location & Privacy. However, this changes all your location and privacy setting back to iOS defaults! Hardly ideal!
With a little digging, I found a less invasive method that. The trust system involves a little handshaking between the iOS device and a Mac. When a user taps the Trust button, macOS stores a file in a special privileged location that contains a variety of digital certificate and encryption key information. The next time the iOS device is plugged in, macOS apparently uses this to send a message back, proving it was trusted previously. Secure terminal connections can be made (for command-line access) in much the same way.
However, the SIM change out—while unrelated to a phone being unlocked for use with a computer—may have changed some state on the phone so that it no longer could validate the proof of trust that my dad’s Mac sent back. There was no error: he just couldn’t access data from the phone. Other folks at online forums have reported a similar situation over several years.
Whatever the precise…