There is a text on the document that is clearly visible and should be recognized easily. However, it is not recognized at all, as shown in the screenshot below.
One of the most common causes of the above behavior is the wrong Marking Type of the Field (Field properties > Recognition tab).
Change the marking type to the proper one. In the case shown on the above screenshot, it should be set to Simple, as the Simple Marking Type represents a text without any marking.
After that, the text is being recognized.