Why didn't my friend receive money sent through Apple Cash?

The other day i was trying to send someone money on apple cash and when i tried to do it it said could not send so i tried again and then it said are you sure u want to send again but the message never sent to them. the money was still taken out of my account and the transaction says complete but they never received the money and it was taken from me.

[Re-Titled by Moderator]

Original Title: apple cash