I'm sorry about the issue. What happens when you download / install the Kindle app on both the iPhone and the MacBook Air computer? Is there any error or message?
Thank you. In the Kindle app of both the phone and computer, did you register / sign in with the exact same Amazon account (same email address) like on the Kindle app of the iPad? Please reply at the box below. Thank you.
No, you need to use the exact Amazon account / email address. Can you please do the following on the iPhone:
Please reply at the box below to continue troubleshooting. Thank you.