Same here on EE esim transfer to new iPhone didn't work. eSIM profile didn't transfer over; the old iPhone remains active with the plan.
I literally tried everything, even using the EE app to scan a new eSIM QR code to the new phone, and kept coming up with an error after imputing a 6-digit code into the EE app: We cannot activate your eSIM plan. Please try again later or call us.
The last option is to request a SIM card. For £1.50 and do it this way one arrives disconnected the physical sim and move it to eSIM what a pain in the backside.