For performance reasons, the default number of visible bars is limited to the last 1000 candles. If you want older data to be visible as well, increase the value of the parameter Maximum number of candles to greater than 1000. You will find this parameter in the indicator settings window - press CTRL+I and click 2x on the indicator name to enter the settings.
Applies to version 4.x - in version 5 the problem no longer exists.
If the Cumulative Volume indicator has been added to the chart but the data does not appear in the window check if the market on the instrument is currently open. If not (e.g. at the weekend or overnight) then wait until the market is open or download and run the MT4Ticker programme. The link to MT4Ticker can be found on our website Useful programmes.