Are my iMessages delivering? Or am I blocked?

So I'm sending messages to a person, and they ALWAYS deliver and they've got read receipts on. Suddenly yesterday, they start having trouble going through when sent on my phone through iMessage. I have to send it as a text suddenly, but when I open my MacBook, the messages are sent as iMessages and they read 'delivered'. So whenever I send a message from my MacBook, it doesn't say delivered, but when I check my phone, its sent as an iMessage and it says delivered, vice versa. Are they actually delivered? Or have I been blocked?