I was excluded from the mother’s coffee morning, and I don’t know why?

It is possible that there was a mistake or miscommunication. It could also be that there were limited spots available and you were not able to attend. It might be helpful to reach out to the person who organized the event and ask for clarification. It is important to remember that everyone has different reasons for making certain decisions and it is best to approach the situation with an open mind and a willingness to understand.