In the chart that shows the bars (the bottom chart), I did not find the line that configures the y-axis scale (eg. a line that calls Axis.setDateScale), but I think the axis is likely to be a date/time axis with the axis range matching the data used for the bars.
When you call Axis.setLabels, it sets the axis to a label based axis. The labels are just names to ChartDirector and have no meaning to ChartDirector. In this case, the y-axis scale will be set to an enumerated scale start from 0. So the first label is at y = 0, the second label is at y = 1 and so on. This scale does not match your bars, so the bars are not visible.
The easiest way to solve the problem is to use another axis for the label table.
' Add another axis to the top for the table
Dim labelAxis As Axis = c.addAxis(Chart.Top, 0)
Dim t As CDMLTable = labelTable.makeLabelTable()
' This is the axis actually used to plot the bars. We hide it so that it does not
' overlap with the label axis.