Several months ago, the only exchange that Nerva (XNV) is currently trading on, TradeOgre made a change to their APIs. This caused a problem with CoinMarketCap, where they stopped tracking trading data.
Coin Market Cap was contacted multiple times by Trade Ogre and Nerva community asking them to fix the issue but they were unwilling to make the necessary changes.
CoinGecko made the changes and is showing trading data. To get market data for Nerva, please visit CoinGecko: