Trying to understand iMessage and its process of activation.

Hi there,

I have an iPhone 5 that works perfectly in every respect when fully tested via the TestM app apart from an intermittent failure on the cellular test (sometimes passing and sometimes failing).

The phone makes calls, receives calls, browses the web via wifi and 4G, sends and receives texts and everything else it should do without fail accept it refuses to register the phone number with iMessage. Emails register without issue. It comes back with the usual activation errors after a period of time and sometimes (but not always) puts an exclamation mark up on the message icon.

I have tried every trick every out there, airplane mode, network resets, full resets, re image in DFU mode and different sim cards (active with credit for calls and texts) to name but a few of the many posted solutions to this problem.

The same sim cards have been tried in other iPhones and activate iMessage without problem so this is not a carrier issue. I have even changed both bottom antenna’s and still no change.

Checking my call records I can see the text messages being sent to Apple for activation but as I understand it the return text message is invisible and that is where the trail goes cold.

Can anybody shed any more light on the process of activation as in how it works in any detail or offer any further suggestions on how to solve the problem?

Any input greatly appreciated.

P.S I am even considering moving the system board into a known good chassis before I put this down to a hardware fault.