Change post order in panel

My client wants to be able to change the order in which posts are displayed on the blog page from the control panel.
At present the ‘change position’ option is greyed out on the panel. How do I activate this please?

If sorting is set to anything but default numbering, the pages cannot be sorted manually: Page blueprint | Kirby CMS

I can change the sorting when I am in the ‘post’ page in the panel, but not from the blog page in the control panel.
What I had really wanted was for the client to be able to drag and drop the posts into position in the blog page.

Then check the settings for the pages section in the blog yaml

Thanks, that was the problem. Works perfectly now.