There is an issue with the Bittrex link on CoinMarketCap, it has been like this for about 2 weeks.
If you go Nexus
https://coinmarketcap.com/currencies/nexus/#charts ,click on Markets, then NXS/BTC on Bittrex is not working, they still have old ticker as well.
Thanks. We were aware when it happened. We requested they change the link for Cryptopia and they also went ahead and updated the Bittrex link without Bittrex making the ticker change.