This error message occurs:
<ConditionData> Validation Failure: Site Id is wrong </ConditionData>
The default DHL integration in Magento has been activated, which cannot be used for shipping from Germany.
Install the DHL extension for Magento. Then make the configuration in the section shown below:
When using the DHL extension, make sure not to enable the section shown below. This refers to DHL in the USA and cannot be used if you are shipping from Germany.