Blocking and unblocking on FB

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Hello,

I messaged a former friend of mine on FB messenger and then I read "can't reply to this conversation." I know that means that I was blocked. They blocked me on messenger but not on FB. I blocked them back and deleted the conversation. Later, I had a change of heart and unblocked them, only to see that once I clicked on them to send a message, I see that I can send a message. Is this because it is a new conversation or because they unblocked me from their end?

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