Are you on iPad or iPhone (iPod touch)? Which iOS? What version of iReal Pro?
In v6, the text button is the one at the bottom of the keyboard called 'abc'. To the left of the text entry box, tap the 3 horizontal lines button for the text menu or just type in 5x.
(Settings>Tutorials>Editor shows the text button.)
Are you saying the 'abc' button is not active and nothing happens when you tap it?