I have accepted an answer to my question, but my reputations didn't increase by 2. Why did that happen?
I haven't reached the daily reputation limit; I think.
You received 2 reputation points by accepting the answer to your question but someone downvoted your post and you got -2 so it didn't show up (i.e. +2 -2 = 0).
Your initial reputation was 101 then you received +10 from an upvote and your reputation became 111 then you accepted the answer and got +2 from that and then someone downvoted your post (-2) so the total reputation became 111.