I have a contact in Messenger that does not friend with me on Facebook. We normally chat without a problem. However, recently my messages are only sent, not received. I don't know if that contact has actually received them or not. That person is still active on Facebook. I still can see the received icon when messaging other contacts.
I also have thought about that person blocks my message (not my entire account since I still can visit their page). However if that's the case, then I shouldn't be able to send anymore messages.
So what is the reason of this?