TEXT highlight not working on PPT / PDF

Hi,
in C#
when i try to set via style a background-color of a text and i go to export it on a PPT or PDF, the backgorund-color was not set.
the code was this:
textFrame.Paragraphs.AddFromHtml(“background color”);

But if i set the color all works fine… so what i can do?
regards

@eXact_learning_solutions,

I have observed your comments. Can you please share source file, sample code and generated result so that we may further investigate to help you out.