Many browsers these days will suspend or 'sleep' browser tabs when they are deemed to be inactive. A tab is generally deemed inactive when the content has not updated for a period of time or if the tab is not in focus.
This feature allows the browser to release PC resources which improved the general performance of the machine it is running on.
This suspend or sleep feature affects the VSM Dashboards when they are not the active browser tab e.g. you have it running in the background. When the browser tab for your dashboard is brought back into focus the browser should release the suspension and your dashboard should start to show live data again, however in some cases the suspension is not immediately removed and you may have to refresh the browser tab to have your dashboard resume.