Six months after J.C. Penney Co. (JCP) launched a bold new pricing plan, customers still aren't buying it. The mid-price department store chain reported a bigger-than-expected loss and plummeting sales during the second quarter, as its customers remain confused by the new pricing strategy that ditched hundreds of sales in favor of every day lower prices. The bleak performance marks the second straight quarter of steep sales declines since the plan was introduced Feb. 1. The company also withdrew its profit guidance for the year. Its shares tumbled more than 8 percent in premarket trading. Penney's poor results, released Friday, underscore how difficult…