I've really been impressed for the last year or two using messages not just on the iphone, but also, desktop, laptop etc.

But someone messages me today asking for directions, and I send those, and then I see ? (on desktop)

Later I call her, she says not received. And in fact the iphone did not have the directions I sent... And this was hour later..

Can this syncing then be trusted at all?

UPdate: sent to her with iphone, and says not delivered in red text. What is issue here? Thans

There are any number of reasons for this including: an error in the target phone number (in my experience this is the most common reason), the target phone number is not associated with a device that can receive text messages, the target device rejected the message, a problem in the telephone network, the target device was offline, the target device could not be contacted, a network error, etc.

Thanks, Joe, well recieved a text from target and was replying. But in any case one of those others.. who knows... You would still trust in most cases replies on desktop they will see on their iphone efficently/ soon? ... one off glitch probably/ hopefully?

All I can do is report my experience which is: replies and/or new text messages from my desktop arrive as expeditiously and reliably as they do from my iPhone or Apple Watch.

FULL DISCLOSURE: the vast majority of text messages I send or receive go through a WiFi connection to the internet regardless of whether they are to or from my desktop, iPhone, iPad, or Apple Watch. About the only time I use the cellular network for data — and texts are data — is when I am driving, and even then my phone is automatically set to NOT accept either phone calls or text messages. (There have been situtations when public WiFi is so bad that I switch it off on my iPhone and used the cellular network instead because it was faster and/or more reliable.)

Using Messages, you cannot text from your desktop computer to an non-iPhone; your Desktop computer does not have cellular.

On your iPhone, do your text messages go to the recipient as green message bubbles? That's a non-iPhone. If they are going as blue (iPhone), then there is something else going on, as joemikeb has expressed.

Not entirely correct. Using Messages you cannot text from a desktop computer to a non-Apple device using the recipient's email address, but in recent versions of Messages you can send a text to a non-Apple device via the recipients phone number using an iPhone that is linked to the same Apple ID. (The iPhone does not have to be turned on.) You can see the details in this Apple support document.

NOTE: You can also configure your desktop Mac to receive voice telephone calls to your cellular phone number. I used to have mine configured to do that but it drove me crazy when a call would come in and my iPhone, Watch, MacBook Pro, and iPad would all start ringing at the same time and no matter which one I answered on the others would still have to ring one more time.

Thanks guy, after 4 years (only) of having a smart phone, now iphone 7; I still do not pay attention to blue or green... or even phone or email; though I know phone is more stable/ better than email.

So she sends me a text, I think she started this.. and I, not paying attention; assuming the desktop, is syncing great respond.

So in future, I try to absorb all this.. and keep an eye out if received. BTW the desktop does not say issue, only SHE and the iphone show/ say issue. I think the dektop should (Apple fault?) say also not received as the phone did...

On my desktop I usually get both the "received" and "not delivered" messages which is not surprising as Apple uses the same code base for Messages on both iOS and MacOS.