Problem

Text using a text style is plotting as a black box when using a pen table.
 

Solution

The pen table is assigning color (0,0,0) to the text element causing the text with a text style that has a background to plot
as a black box. Add the statement fill_color=(255,255,255) to the pen table to keep the background white causing the mask appearance.

The text must be a Bentley font and not filled for this to work.