He stopped talking to me then wished me happy birthday, why?

I was talking to a guy consistently and one day he stopped talking to me over something very very VERY small. He was ignoring me for days so I told him how mad I was at him for it. My birthday came around a week later and he wished me happy birthday and asked me for my cash app to send me money. I said thanks and sent him my cash app. He didn’t respond nor send me money. I’m not worried about the money, I just don’t understand why he did that

He stopped talking to me then wished me happy birthday, why?
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