Unable to activate
I am facing problem after updating mobile to ios 12..... error shows " an update is required to activate your phone "
Imei number is not showing..
Only serial number is showing...
iPhone 5s
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First Contact your agency who provided you the SIM
If you can't activate your iPhone
If your iPhone can't be activated or an alert says the activation server is unavailable or the SIM card is unsupported, learn what to do.
Check these things first
- If an error says, "No SIM" or "Invalid SIM," learn what to do.
- If asked to sign in with an Apple ID during activation, learn about Activation Lock.
Still need help? Use the next section.
Follow these steps
- Check the list on the System Status page. If the box by iOS Device Activation isn't green, try to activate your iPhone later.
- If asked to enter your password as you activate your iPhone, enter the password. (A password prompt means that Activation Lock might be enabled in Find My iPhone.)
- Restart your iPhone.
- If you're using a cellular data connection, connect to a reliable Wi-Fi network instead.
If you still can't activate, here's how to activate your iPhone through iTunes instead:
- Make sure that you have the latest version of iTunes.
- Check that your computer has an Internet connection.
- Open iTunes on your computer. With the cable that came with your iPhone, connect your iPhone to your computer.
- Wait while iTunes detects and activates your iPhone:
- If iTunes shows, "Set up as New" or "Restore from Backup," it means that iTunes activated your iPhone.
- If an error in iTunes says that the SIM card isn't compatible, contact your carrier.
Get more help
- To check for network or activation issues and see if you need to replace your SIM card, contact your carrier.
- Use recovery mode to restore your iPhone.
If restoring your iPhone still doesn't work, contact Apple Support.
If you can't activate your iPhone - Apple Support
https://support.apple.com/en-us/HT201407