Sort:  

Two possible reasons as far as I know:
a) It's been down for a few days - but I got a busy upvote again late yesterday so that should hopefully be fixed now
(b) You need a minimum amount of follower power - here's a great analysis from @crokkon and in the comments it explains how to test that:
https://busy.org/utopian-io/@crokkon/the-busy-org-free-upvote-bot-adoption-by-users-and-performance-since-nov-2017

Hope that helps!

Earlier bot was voting me but from last many posts that was not voting.

Coin Marketplace

STEEM 0.09
TRX 0.31
JST 0.034
BTC 111214.75
ETH 3958.59
USDT 1.00
SBD 0.60