Please ensure that the platform is connected to the Internet (check the connection status in the bottom right corner of the platform window as it should display, for example, 1234/1). If a low value such as 23/0 is displayed in the bottom right corner of the platform, then your Internet connection is slow and you will have to allow a couple of minutes for the platform to update the charts and the price feed. You can also try right clicking on the requested pair, then on chart window.
Bear in mind that the more charts you have open, the slower the platform will update, due to the high number of records which need to be displayed on the platform. Consider leaving open only the chart which you are using.