How come my crush didn't smile back when I smiled at him? Good or bad?

So he's a shy guy I'm a shy girl so I know how it feels like to express yourself to somebody you're crazy about, but anyways we lock eyes everyday for about 3+ seconds , it feels like everything goes in slow motion when we lock eyes.. But anyways getting back to the original question, so last week I finally built up courage to smile at my crush , that was suppose to tell him "I like you but I'm shy" we locked eyes for 5 seconds.. While we locked eyes and I was smiling, he didn't smile back☹ and no there was nothing on my face/teeth. He had this expressionless face as always but he had a shock look in his eyes at the same time. Since that incident happened I've been ignoring his presence out of embarrassment. how come he didn't smile back? Is he too shy? Is he not interested?
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I forgot to mention we've been locking eyes every single day for the past 2 months!!!
How come my crush didn't smile back when I smiled at him? Good or bad?
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