Why did my male co-worker started treating me differently?

Anonymous

We are in the same team and we discovered we had a lot in common, basically male version of me, and he used to be very attentive, teased me a lot, tried to make me feel included and asked me about stuff.

Now we still have friendly conversations here and there but it's mostly work related and it's not what it used to be. He answers mostly using emojis when normally he'd send a long text, doesn't ask me anything and overall it feels like I'm just someone who's "there". Also I'm mostly the one who's initiating conversations.

I don't really want to ask him personally because I may be the only one who's feeling like that and it'd be awkward so do you guys have any reasons you'd suddenly stopped being so attentive towards your female coworker?

Updates
1 mo
Just to clarify, HR didn't get involved for sure. He didn't tease me any more than some other have nor he has a girlfriend. He's a workaholic and he quite regularly says he wants to find someone. I'm also the only girl in the team.
I agree though that I might have come off as uninterested because that's what I do when I like someone. I tend to be way more cautious around them because I feel like everything I do scream "I like you".
Thank you all for your opinions.
Why did my male co-worker started treating me differently?
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