Is there a known error on facebook where the person does not receive your message at all?

[Shivam]

I was chatting with someone on facebook, when i sent a message and the "seen" notification never came. It has been around a month and i still haven't got a reply. So i'm not sure whether the message was actually delivered.

[Daniel]

There is No Known Error Of That At All If The Seen As Has Not Been Recorded That Does Not Mean That There Person Didint Get it it Means The Person Did Not Open The Message Or Has Not Been on Facebook in a While

[Barbie]

I think he didnt open your chat. If you have doubt send a hi, then he will get a message notification