What template are you using?
Pages > Menu > File > New From Template Chooser > Word Processing or Page Layout
If you choose a blank Word Processing template, type away to your heart's content.
If you choose a Page Layout template (Blank Canvas) it will open a new document with nothing at all on the canvas. You must insert a Text Box or a Shape to contain your typing. Think of this as a mimic for a drawing app. (you insert objects on to a blank canvas).