It can take days after a round is ended for the coin to mature and be traded. So you have to be patient. I suspect that it won't always be like this but for now it is what it is.
so why is hashcows so slow to do it ? when others arent even coinsolver a smaller pool converts the coins the same day.
It's the coin, not hashcows. I was thinking the same about a week ago when I tried hashcows out, and a few days after I started getting payments for the days before when I mined. So don't worry, you'll get what you mined.