Merx Starterkit / E-commerce (cart problem)

I’m trying to get Merx Starterkit to work.
You need PHP8 minimum, on PHP7… it didn’t work.

I seem to still get an error, my cart doesn’t fill up…
Anyone know how I might solve this?

I follow the installation and didn’t touch the code (except for the HTTPS in .htaccess)

Have you tried to set the RewriteBase to your root (/merx-starterkit) – Line 22 in .htaccess.