The "Market is closed" error message indicates that the product you want to trade is not within the tradable period. This typically occurs on weekends, market holidays, or other times when the relevant market is closed, preventing you from trading or modifying orders.
To check the trading period of a product, right-click the market quotation window, select the product, and then choose "Specifications." The trading period of the product will be displayed at the bottom of contract details.

