Why is he suddenly ignoring me?

I like this guy and we've been friends since forever. Talk, text, Netflix and chill. However, he's been kinda distant with me recently. We haven't texted since last week (ended the convo in good terms btw) and he's been ignoring my 'My Story' Snapchats that i post (and he ALWAYS looks at them). Why do guys do this? Why the sudden distance?
Why is he suddenly ignoring me?
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