Blockbase and HEIWA

Before we start: Though Heiwa is a child theme to Blockbase, made for wp.org it is clearly stated, that the site is working on self-hosted WP, too.

Question:

The theme can´t be installed in WP at my WP-Installation (new one).

By installation it says that Blockbase is necessary to be installed before,
but this has already happend and nothing changed: The themestill does not show up in order to be activated.

What´s the problem here?

Thank you.

The page I need help with: [log in to see the link]