[JM19]

My daughter’s iPhone 12 has no cellular connectivity. Works fine on wifi. I tried hard reboot. Tried removing and reinserting SIM card. None of those worked.

In Settings>Cellular shows Error.

It was working fine and all of a sudden out of no where this started happening.

Anybody else experienced this? If so, what fixed it? Thanks.

[Up_And_Away]

If you performed a reboot, plus removed/visually checked for lint etc/put the Sim back in but this didn’t fix it, I’d call the carrier asap. If you’re paying AT&T then it is on them to make their SIM card work. A smartphone is a handheld Wi-Fi device without the Sim. And the Sim is a Carrier device, it’s what makes a phone part of and capable of using a cellular network.
But it definitely wouldn’t hurt to check out the applicable Apple Support document:
https://support.apple.com/en-us/HT201415

I see AT&T which, I’m pretty sure-ish, you can (same size) put into another iPhone that is unlocked or locked to AT&T. If you have such a device nearby and can test this, and get the same results, the Sim is bad or the carrier has some issue with the Account. But I’d stick to calling the carrier support.

[Annie_M]

I agree that contacting your carrier is the best course of action.

[Ed7789]

Two other things you could try:
1. Make sure that cellular settings list 4G (sometimes called LTE) as enabled
2. Try resetting Network Settings, in General, Reset. This will erase all network settings (Wi-Fi, Bluetooth, and Cellula) and start them back from defaults.

[Annie_M]

One other thought... have you looked to see if there is an update to your Carrier Settings? My husband once had an issue where he had no cellular, and we checked to see if there was an update available and there was. That fixed his issue.

Here's how

[Just_Me_D]

In the Cellular Settings, please make sure the appropriate cellular plan is enabled.

[Quis89]

Sometimes you can toggle Airplane mode off and back on and a quick thing to try. Though if you've done the other suggestions in this thread, I doubt that will clear it.

You'll likely need to work with your carrier.

[JM19]

Been meaning to update post with findings. So pretty much the iPhone was faulty. First I dealt with ATT support. Determined the problem was not with the carrier. SIM card worked on another iPhone. Then dealt with Apple support.

They had me try updating/restoring the iPhone via iTunes connected to computer. That didn’t work. Ended up taking the iPhone to Apple Store. They tried doing just about the same to no avail. They replaced the iPhone. Replacement should be arriving in the mail next week.

Thanks to all who replied.

[Just_Me_D]

Been meaning to update post with findings. So pretty much the iPhone was faulty. First I dealt with ATT support. Determined the problem was not with the carrier. SIM card worked on another iPhone. Then dealt with Apple support.

They had me try updating/restoring the iPhone via iTunes connected to computer. That didn’t work. Ended up taking the iPhone to Apple Store. They tried doing just about the same to no avail. They replaced the iPhone. Replacement should be arriving in the mail next week.

Thanks to all who replied.

On behalf of those who replied, you’re very welcome and thank you for the update.

[Annie_M]

I am so happy that you have had your issues resolved. Keep us posted when your new iPhone arrives!