This error may show if you are trying to install an eSIM on a network-locked device. 
You can check if your device is locked by following the steps below:
- Go to Settings > General, and tap About.
- Under Carrier Lock, you should see a message that says No SIM restrictions. If you don't see that message, please contact your carrier to have your device unlocked.
If you have confirmed with your current provider that your device is unlocked, please contact support.