My iPhone won't trust this computer
The "Trust This Computer?" prompt never appears. Or it appeared, you tapped Don't Trust, and now it will not ask again. Or it keeps appearing every single time you plug the phone in.
Trust is a grant the phone stores about one particular computer. It is created over a cable, with the phone unlocked, and confirmed with the phone's passcode. Miss any one of those three and iOS does not ask.
01What the grant actually is
When an iPhone is connected to a computer it has not seen before, iOS asks whether that computer may talk to it as more than a charger. Approving it creates a pairing record — a key exchange, stored on the phone and on the Mac — and until that record exists the phone answers nothing.
This is Apple's mechanism, not ours. It is the same prompt you get plugging a phone into Xcode, Apple Configurator, or Finder, and GPSLarp needs it for the same reason those do: it drives the phone over Apple's own device-development protocol.
02The prompt never appears
01Unlock the phone first, then plug it in
A locked iPhone does not show this prompt. Unlock it, leave it on the Home Screen, and then connect the cable. If it locked itself while you were finding the cable, unlock it again and unplug and replug.
02Use a cable that carries data
Plenty of cables sold as charging cables have no data lines in them at all. The phone charges, the Mac sees nothing, and no prompt appears on either device — which is indistinguishable from a broken phone until you swap the cable. Try a different cable and a different port before anything more drastic.
03Look on the phone, not on the Mac
The prompt is on the iPhone's screen. If the phone is face down, in a pocket, or on a Focus mode that suppresses banners, it can be sitting there unanswered while you watch the Mac and conclude nothing happened.
03You tapped Don't Trust
iOS records that answer and stops asking. Reconnecting the cable does not bring the prompt back, and neither does restarting either device — which is what makes this the most frustrating version of the problem.
01Try the simple version first
Unplug the cable, lock the phone, unlock it again, and plug it back in with the phone unlocked and awake. On some iOS versions this is enough to re-ask. It costs ten seconds, and the alternative below costs rather more, so it is worth trying twice.
02Reset the phone's trusted computers
On the iPhone: Settings › General › Transfer or Reset iPhone › Reset › Reset Location & Privacy. Confirm with the passcode. Then plug the phone into the Mac with the phone unlocked, and the prompt comes back.
Read this before you tap it
Despite the name, that reset does two things. It clears the trust record for every computer the phone has ever been paired with, not only this Mac — so any other machine you use it with will ask again. And it resets the location and privacy permissions you have granted to apps on the phone, so apps will re-ask for location, photos, contacts and the rest. Nothing is deleted, but you will spend a few minutes granting permissions back.
04It asks every single time
A pairing that is created and then immediately forgotten usually means the record is not being written. Two things produce that:
- The passcode step never completed. Tapping Trust starts the pairing; entering the passcode finishes it. Dismissing the passcode prompt leaves the phone in the state it was in before, and it will ask again next time.
- An intermittent cable or port. A connection that drops mid-handshake can leave the pairing half-made. This is the same swap-the- cable advice as above, and it is above for a reason: it is the answer more often than it deserves to be.
05If that did not work
Once the trust prompt has been answered and the passcode entered, the pairing exists and GPSLarp has what it needs from this step. If the phone still does not appear in the app after that, the remaining causes are the ones on GPSLarp can't find my iPhone — the network, the search window, and on iOS 16 or later Developer Mode, which is a separate switch that this prompt does not turn on.
Worth being straight about the limit of this page: it describes what iOS does. Whether your particular phone and your particular Mac get through it is something nobody here can see, and no iOS version has been tested against this product.