Why live messenger is not letting me chat with my contact who is on IM?

There could be several reasons why Live Messenger is not allowing you to chat with your contact who is online. Your contact may have blocked you, or they might have privacy settings that prevent them from receiving messages from you. Additionally, there could be connectivity issues or problems with the application itself. It's also worth checking if your contact is set to "Do Not Disturb" or is experiencing issues with their account.