Why was my guy friend upset when I couldn’t stay late for his birthday?

We’ve exchanged jewelry by the way. He wears my bracelet Cuban, and I have his Cuban chain. Wore my bracelet that night as well! Mind you, a girl is in the group setting with along with the others and she really likes him and spends time with him all the time but he’s upset with me?
Why was my guy friend upset when I couldn’t stay late for his birthday?
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