We have recently been informed by our SMS provider that people on the Virgin Mobile network are unable to reply to certain numbers which is why some of your clients may report that their reply doesn't send and they see "failed".
Since being informed of this, we are looking into changing the phone number that our text reminders come from so that Virgin users are able to reply to these.
My client isn't on Virgin and still can't reply to the text?
Occasionally you may come across clients clients on other networks who say they weren't able to reply to their text reminder and instead they may see "failed" when they try to reply.
Unfortunately this is not something in our control. It is due to something specific to the client's phone - usually for one of these reasons:
They don't have phone signal (must be phone network, not just internet)
They don't have any phone credit
Their phone network has disabled their ability to reply to numbers like this
Regrettably there is nothing we can do to enable their reply to send (if we could, we would!) so it's best to just try again next time or ask that they contact their network provider.