It sounds like your iPhone 12 should support eSIM, but since the "Add eSIM" option is missing, here are some steps you can try to resolve the issue:
1. Check if Your Carrier Supports eSIM
Even though you previously downloaded an eSIM, it's possible that your carrier has disabled it or your plan no longer supports it. Contact your carrier to confirm eSIM compatibility and request a new eSIM activation.
2. Ensure Your iPhone is Unlocked
If your iPhone is locked to a specific carrier, you may not see the "Add eSIM" option unless it’s unlocked.
Go to Settings > General > About and scroll down to "Network Provider Lock." If it says "No SIM restrictions," your phone is unlocked. If not, contact your carrier.
3. Update Your iPhone to the Latest iOS Version
Go to Settings > General > Software Update and ensure your device is running the latest iOS version.
4. Reset Network Settings (If Not Already Done)
Since you’ve already tried this, you can also try a full Reset All Settings:
Go to Settings > General > Transfer or Reset iPhone > Reset > Reset All Settings.
(This won’t delete your data but will reset settings like Wi-Fi passwords and VPN configurations.)
5. Manually Enter eSIM Details
If your carrier provides eSIM activation details (SM-DP+ Address and Activation Code), you can try adding it manually:
- Go to Settings > Mobile Data (or Cellular) > Add Mobile Data Plan
- Tap Enter Details Manually and input the details from your carrier.
6. Try a Fresh eSIM Activation
If the previous eSIM stopped working, it may have been deactivated. Contact your carrier and ask them to issue a new eSIM QR code or activation link. Then follow these steps:
- Go to Settings > Mobile Service > Add eSIM (if available).
- Scan the QR code from your carrier.
If none of these steps work, your carrier may need to reset eSIM provisioning for your number.