When using stops on a stock like SNPK, you have to use a stop loss entry and a market order.  If you had the stop set for 2.00 and to sell at 2.00, the ask may have already quickly moved past that so you order is there at 2.00, with the ask being 1.90 - you will not get filled.  Some allow you to set a stop at a specific price with a variable but on a stock like this, set the stop and use a market order to protect yourself when the stock begins a rapid decline lilke this did.