Messages sent but not delivered on FB messenger

Hello all,

I have a question: a friend of mine on FB and I have been sending messages to each others back and forth for a while now. However, after some point, the messages have been marked as sent (white checked circle) but not delivered (blue checked circle) even when my friend is online. The messages are switched directly to "seen" just before my friend replies. Why is that happening?

Thanks

 

When your friend directly open your message that time show it seen, Other wise never it will be seen if friends online always.

 

Yes, but sometimes my friend is online and the circle remains white. It will be "seen" only just before they want to reply. Is there any possibility that my conversation has been moved to the "other" folder, or marked as a "spam" by them?

 

yes . there is an option check the attachment

 

I am not looking for the options, I am asking if they have done something like this to my conversation, so that my messages aren't delivered even if the person is online.

 

must be a bug, it'll be alright

 

I have faced this problem many times. I just choose other messengers to communicate with friends.