Contents is entering just fine, but your template has changed the text to white on a white background. Culprit CSS as follows.
IN: templates/rt_hybrid_j16/css/header4.css
ON: Line 10
Code:
#rt-header-surround, #rt-header, #rt-drawer, #rt-top, #rt-header-surround .title span, #rt-header-surround .inputbox {
color: #FFFFFF;
}
The above is forcing all inputs in the header position to have a color of white.