There could be a few different things causing this. First off, try refreshing your chart by holding down the Ctrl key, and clicking on the green OK in the Cursor Window. You may need to turn on the Cursor Window by going to Chart Options --> Cursor --> Cursor Window. If that doesn't work, then try closing eSignal and opening it back up. If that is still unsuccessful, then there could be something wrong in the Time Template, and I would suggest a using different Time Template (or just create a new one if you are familiar with that process.) To change Time Templates, click on Chart Options --> Time Templates --> [choose one].
Finally, if none of these correct the problem, then there could be a corrupt chart on our hands. Try closing the Advanced Chart Window, and create a new one by going to File --> New --> Advanced Chart --> Default Chart