The error (DHL Validation Failed: ErrorCode: 420505 Data: The destination location is invalid. Please check the data) from DHL occurs when there is an issue with the destination address.
To resolve this, follow these steps:
Click Orders then Overview.
Find the order.
Click Action then Details.
In the Order Details page, check and correct the following:
Ensure the address format is correct (for example, the city may be in the wrong field)
Make sure there is no missing information in the delivery address
If the address contains non-English or special characters, the courier may not accept it
Verify that the address exists and is valid
Finally, retry generating the shipment.