(Child) Theme changes don't appear on site

I just installed DT on my site Tierschutz-adressen.de.

Then I installed child themes Techflow and Heatmap in /wp-content/themes/ but none of them work. Instead of the initial “Template: [xxx]” I changed that value to “Template: DT” like you describe it. Doesn’t help.

I had to change the child’s template name to “Template: directorypress” to get it activated but guess this is wrong. However: Heatwave should be activated now, that’s at least what WP tells me. But it doesn’t show up….

Uploading the child theme to DirectoryPress > General Setup doesn’t work either. Confusing …