Align dimension test with dimension line

Elice

I am trying to align my dimension text so that it is centred on the dimension line, so I have gone into Settings>Dimensions>Text and changed both "Text pos vert" and "Test pos hor" to centered but as soon as I do, the text on my dimensions disappear. Has anyone encountered this problem?

Roy Klein Gebbinck

Most likely the text is there but hard to detect because it is very small.