Hi,
The first to check is the Text color,
a) Select the frame in which you have the problem, if it's in the complete document then don't select anything
b) Go to "Color" panel
c) Click on "T" icon (marked with yellow arrow)
d) Check the color of the text in the box ( marked with red arrow). To change the color , double-click on it to open color picker and select your color.
- Manish