How to Fix iPhone 17 Cellular Data Not Working After iOS 26.3 Update

iPhone 17 Cellular Data Not Working After iOS 26.3 Update usually means the line settings need to refresh, a carrier update is missing, or the eSIM or network stack broke during the update.

For related help, also see the iPhone 17 hub, How to Fix iPhone 17 WiFi Keeps Disconnecting After iOS 26.3 Update, How to Fix iPhone 17 FaceTime Not Working After iOS 26.3 Update, and How to Fix iPhone 17 WhatsApp Calls Not Working After iOS 26.3 Update.

Fix #1: Toggle Airplane Mode and restart the iPhone

This forces the modem to reconnect cleanly after the update.

1. Turn Airplane Mode on for 30 seconds.
2. Turn it off again.
3. Restart the iPhone 17.

Fix #2: Confirm the correct cellular line is active

Dual SIM and eSIM settings can change after a major iOS update.

1. Open Settings > Cellular.
2. Make sure Cellular Data is enabled.
3. Choose the correct voice and data line if you use more than one.

Fix #3: Install a carrier settings update

Carrier bundles often fix data and eSIM bugs after a new iOS release.

1. Go to Settings > General > About.
2. Wait a few seconds for a carrier update prompt.
3. Install it if one appears.

Fix #4: Disable VPN and reset the network session

VPN profiles and stale network settings can block mobile data.

1. Turn off any VPN app or profile.
2. Go to Settings > General > Transfer or Reset iPhone > Reset.
3. Tap Reset Network Settings.

Fix #5: Check eSIM or physical SIM status

If the update damaged the line profile, the phone may show bars but no working data.

1. Open Settings > Cellular and inspect the active line.
2. Reinsert the physical SIM if you use one.
3. Contact the carrier before deleting and re-adding an eSIM.

Fix #6: Test LTE and 5G settings

Some post-update data issues clear up when you change network mode temporarily.

1. Open Settings > Cellular > Cellular Data Options.
2. Switch between 5G Auto, 5G On, and LTE.
3. Test Safari or Maps after each change.

Fix #7: Update iOS again or contact the carrier

If the problem began with iOS 26.3, Apple or your carrier may already have a follow-up fix.

1. Go to Settings > General > Software Update.
2. Install any newer version available.
3. If data still fails, ask the carrier to reprovision the line.

If cellular data is still not working, browse the main iPhone 17 page for more related fixes.