Like many other iPhone users, I upgraded to IOS 7 pretty much as soon as it came out.

There’s a subtle bug that seems to be impacting many people who upgraded early in the piece, such that iMessage has lost its internal ‘permission’ to use your mobile number as the source of iMessages transmitted over the Internet.

People aren’t necessarily picking up on this issue by themselves, because their problem isn’t actually visible to them. It is only visible to (and only a problem for) the other IOS users that they exchange messages with. It just lurks there, driving people batty, with necessarily having an obvious underlying cause.

I’ve written this post to explain the issue and how to fix it, mostly so I can tell my own friends about it without repeating myself constantly. I hope its also useful for others in the same way!

The root cause

Once the IOS 7 upgrade is done, in many cases (including for me), the association between your mobile number and your iMessage account was silently broken (de-activated) during the upgrade. 

An aside about iMessage: IOS tries to use the Internet to send messages to others if it can, to short-cut around the mobile network. It ‘falls back’ to using SMS (costing you money) if the Internet path isn’t available to use. This test is done in each direction separately, and the outcome can be different in each direction and can be different even for successive messages.

The outcome is indicated to you via colour coding. If your message is rendered in blue text, then its been transmitted using the Internet, and if it is rendered in green text, then the message has been sent using SMS over the cellular mobile network.

If your text turns from green to blue while you’re busy typing it in, that means IOS has figured out (in the background) that your destination is ‘Internet accessible’ and it plans to use the Internet path to send it. If your text turns from blue to green, while you’re typing or after you hit send, then the Internet path didn’t work out after all, and IOS has ‘fallen back’ to using an SMS instead. 

Manifestation

This is how people with IOS see your iMessage conversations, if this problem is present:

• People sending messages to your mobile number from another IOS device are not  permitted to send them via the Internet (forcing the messages to be sent as SMS)
• Replies from your phone get sent back using another one of your iMessage identities as the sender name (e.g. from one of your email addresses), rather than (ever) coming back as being from your mobile number.

This costs your correspondents money (because they’re having to use SMS to reach you).

It also causes confusion for them because your replies come back from a different name/place, and this makes them appear in a separate iMessage conversation stream, disjoint from the window they used to send messages out to you.

This can also generate scenarios where you can’t successfully reply in turn, if your own outbound Internet path or that of your correspondent then becomes unavailable – because iMessage isn’t then able to fall back to using an SMS to send to the mobile number.

Long story short – confusion reigns and messages can go awry in various ways.

The process of making that association in the first place was done automatically via IOS sending itself an SMS message, to prove to itself that your number really is ‘you‘. 

For whatever reason, the IOS 7 upgrade has silently broken that association and it doesn’t manage to automatically heal it again without your intervention. 

The fix

Fortunately, the actual fix (once you appreciate the problem exists!) is easy.

On your iPhone, go into Settings -> Messages and you’ll see this control panel.

iMessage will show up as being ‘on’ (green) at the top of that panel.

No apparent issues here, but we need to dig just a little bit deeper.

Press the text to the right of ‘Send & Receive’. In my example, this says ‘2 Addresses >’. For you, that number could be different.

When you tap on that text, you’ll get a detailed information panel for your iMessage account, which looks something like the next image.

Here is where the issue becomes visible.

If you don’t have a tick beside your mobile number in the centre panel (‘you can be reached by iMessage at’) on that page, then iMessage isn’t considering itself authorised to use that number for Internet-based messaging.

It also won’t allow you to configure your mobile number to be the place to ‘Start new conversations from’ in the lower panel on that page, for the same reason.

Ok, now you can see the problem, whats the fix?

Its easy – and in the classic style of many computer related problems, it is a simple matter of ‘turn it off and on again’:

• Return to the previous panel (where the iMessage on/off switch is located)
• Turn iMessage off by using the toggle beside ‘iMessage’ at the top of that page.
• Turn iMessage back on again, by pressing that toggle once more.
• When you turn it on, your screen will say ‘Waiting for activation…’ for a few seconds, and then (hopefully!) iMessage will turn on again.

A little bit of background magic has now happened – magic that clearly didn’t happen properly during the upgrade to IOS 7.

Specifically, IOS has quietly sent itself a fresh authentication-checking SMS message, to prove to itself (and to Apple) that you do really ‘own’ that mobile number and hence that you’re authorised to use it in messaging.

If you  return to the deeper configuration panel, you will see that there is now a check box beside your mobile number under  ‘You can be reached by iMessage at’.

In addition, you can (and should) now select your mobile number in the lower pane, as the source to start new conversations from.

Bingo – the resulting asymmetric data path has been healed, and all is right with the (iMessage) world again, in terms of conversations involving you 🙂