This is stemming from bad coding. Your theme has the following definition for the table header (th) elements (line 86 of style.css):
th {background-color: #666; padding: 10px 10px; border-color: #666; font-weight: bold; color: #FFF; }
So the table header is suppose to be grey color and have white font but on line 370 of style.css file it has the following CSS:
#pricing_table td, tr, th { background:none; border:none; text-align:center;}
This is making the table header inside the “pricing_table” div to have no background. Now for some reason (most likely this whole page is wrapped inside that pricing_table div) your site is taking the definition of this table header background and making it an empty background with white font (so you are seeing white on white).
Basically, if you place a table inside your WordPress post or page it won’t have any table header background while the font color is defined as white (#FFF)!
Try changing the following line (line 86 of style.css file of the theme):
th {background-color: #666; padding: 10px 10px; border-color: #666; font-weight: bold; color: #FFF; }
to the following:
th {background-color: #666 !important; padding: 10px 10px; border-color: #666; font-weight: bold; color: #FFF; }