Make sure you don't just have a buy order in. You have to remember you are basically selling your BCH to a person in return for his ETH. So if you have a buy order in to sell, for example, 10 BCH for 100 ETH at $300 an Eth(just made up numbers), then you're not going to get that order completed because nobody is selling their ETH for that price. You would have to increase it to around whatever the current price for eth is ($335). Or you can leave it at $300 and wait and hope it goes back down there, then someone will buy your BCH for the price of eth you are willing to pay.