Why are my editing commands not working ? Split, mark etc

Why do my edit commands not work ?
I click on the marker, split or whatever and nothing happens.
I’ve had that working before.

I have the file open & edit is selected at the top right.
I cannot place markers either with it playing or paused. I watch video tutorials, but all seem to assume everything just works.
I presume I’m missing some really simple setting, but google does not find the answer.
I’m new to video editing, but have done a lot of audio editing with audacity.

Shotcut version 25.03.29 on Windows 10.