Objects (lines, dimensions, fill, etc.) are displayed in teh order in which they are created. If a solid fill is created last, it covers anything that occupies the same space. The display order of the objects can be changed. On the Home tab there is an Arrange command group. In this command group there are commands like Bring to Front and Send to back. These commands are used to rearrange or change the display order of the objects. In this case select the fill and run the Send to Back command. It will now display behind everything else.
Sometimes you may want geometry that is behind the dimension to not bleed through the display of the dimension text. In other words you want the text to cover everything behind. To do this go to the dimension style and on the Text tab check the 'Fill text with background color' property.