Why did my fb messenger app yesterday stop delivering my messages to one person but not everyone else it was working fine yesterday and then at 8pm started sending and not delivered my messages?

There could be several reasons why your Facebook Messenger app stopped delivering messages to one specific person. The recipient may have turned off their notifications, blocked you, or their account could be experiencing issues. It's also possible that there was a temporary glitch in the app itself. Try restarting the app or checking your internet connection to see if that resolves the issue.