aka.ms/addAccount — turn on iPhone ↔ PC file sharing

Android at least fails loudly here: sign in on the phone with a Microsoft account that differs from the PC's, and the PC never moves — the pairing that looks finished but never happened. iPhone gives you no such warning. Pair with a mismatched account and the link completes normally on both sides. Calls, messages, notifications and battery all appear and keep working. Nothing looks wrong, and nothing tells you anything is.

The gap only surfaces the first time you try to move a file. Right-click something on the PC, choose Send to phone, and instead of sending you get: "Share files between [your] iPhone and PC — To set up file sharing now, sign in with your account on both your devices," showing the account name and a Switch account option, with Continue and Maybe later. Maybe later does exactly nothing — the window closes and the file is never sent.

Continue leads to "Share your files between your iPhone and PC" with a QR code that expires in 3 minutes and the instruction that matters: once Link to Windows is open, sign in with the same Microsoft account used with Phone Link. Choose Continue without a QR code and you land on "Set up your iPhone and PC manually" — open a browser on the iPhone, go to aka.ms/linkAccount, install or open Link to Windows, and sign in with the account named on screen. That's the manual path below, arrived at from a different direction.

Going the other way, the message is actively misleading. Share a file from the iPhone by picking Link to Windows in the share sheet and it behaves as though all is well: your PC's name appears in the list, you select it, the transfer starts loading — and then it fails with "File failed to send. We are unable to reach LAPTOP-NAME. Please make sure your PC is unblocked and try again." Nothing there is true of your PC. It isn't blocked, it isn't unreachable, and nothing on it needs changing; the fault is the mismatched account on the iPhone. Follow that message and you'll spend the evening on firewalls, Bluetooth and network settings without ever getting near the cause.

Why this matters more than it looks: because everything else works, the mismatch can sit undetected for weeks until the day you actually need to send a file. If file sharing has never worked on an otherwise healthy iPhone link, check the account on both devices before troubleshooting anything else.