Impress: horizontal alignment in text box does not work?

I am new to Impress and try to find my way around.
I created a text box on a slide and want to align the text in the box (horizontally centered). I go to format text/align text/center, but nothing happens.
Vertical alignment (top/center/bottom) on the other hand does work…

Any suggestions would be much appreciated…

You must select the text, not the frame.

That’s what I did,…

First steps to take before submitting a bug

Thanks for taking time to help out. Looking at these first steps, they are related to reproducing the error in the latest version of Impress… However, I installed it yesterday, so would think that is the latest version? And my question popped up after using it for about 10 mins - could my user profile be corrupted by then?
The weird thing is, the vertical alignment does work…