In the configuration for the participation numbers (German: Teilnahmenummern) the DHL products are missing in the menu.
Usually, things like "DHL Paket V01PAK" etc. should be shown here.
The origin address of the shop is not configured correctly.
Make sure the shipping origin address of the shop is configured correctly in the section "Sales -> Shipping settings -> Origin". The country is especially important.
After correcting the settings, you need to flush the Magento caches.