MTN's system is not allowing for an eSIM to be moved to another device. This needs to be looked into by them. Afrigirl has said this more than once.
To get a new QR code created for the new device you just need to send a photo of you holding your ID with a piece of paper with the date on it to
[email protected]
You can then give the ticket ID you get in reply to Afrigirl or the whatsapp guys and they will escalate it to the Air Mobile admin team to do it for you. It does not take long and it is not hard.
I know it is a schlep but it can be done.