Question TextMeshPro not showing in screen space overlay

I have some text to display numbers in my scene and it works in worldspace:



But, as soon as I switch to screenspace overlay it does not show any more:



What am I doing wrong?

The background color of the circle is normally red but in worldspace it shows at orange.

 

I didn't find a solution with TextMeshPro so I removed it and used pre-made sprites instead.