can't approve new iPhone

If you lost the trusted device or phone number associated with your Apple ID

As long as you still have your Recovery Key and remember your Apple ID password, you can sign in and add a new trusted device or phone number to your account. You can also remove any devices you may have lost, sold, or given away.

1. Go to your Apple ID account page and enter your Apple ID and password.
2. On the Verify Your Identity screen, select "Can’t access your trusted devices?"
3. In the pop-up window, enter your Recovery Key.
4. Go to the Security section and click Edit.

Remove the device you no longer wish to use to verify your identity. If you have additional devices with Find My iPhone enabled, you can verify them as trusted devices. You can also add additional trusted phone numbers.

If you lost your Recovery Key

As long as you remember your Apple ID password and still have access to one of your trusted devices, you can sign in and create a new Recovery Key.

1. Go to your Apple ID account page.
2. Sign in with your password and trusted device.
3. In the Security section, click Edit > Replace Lost Key.

Keep your new Recovery Key in a safe place. Your old Recovery Key won't work anymore and you can't use it to reset your password or access your account.

If you can't sign in with two-step verification using your Apple ID ...

https://support.apple.com/en-in/HT202649

In order to approve your iPhone, you need to have access to another iOS device that already has iCloud keychain enabled. If you don't, then you'll need to choose "can't approve" and follow the on screen steps to reset your "end to end encrypted data.