i left some unit on Bittrex,i send it to cryptopia,bittrex had a txid ,but i can't find the coins on cryptopia or otherwhere,what should do to the coins on bittrex?
What you should do is learn that both Bittrex and Cryptopia are private companies and your private dealings with them have nothing to do with the currency. Once you learn that, then you'll know which private company to go to in order to solve your private transaction issues.