Please make sure 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 eg. 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.
Bear in mind that the more charts you have open, the slower the platform will update, due to a high number of records which need to be displayed on the platform.
Please leave open only the chart which you are using.