The error (Ship Web Service Error Message: An exception has been raised as a result of client data. InnerMessage:Hard120110Missing or invalid Shipper AttentionName) from UPS occurs when the client selected for shipping is missing its contact name. To resolve this issue:
Click Clients then Overview.
Search for the relevant client.
Click Actions then Edit.
Ensure the Contact Name field is populated.
By following these steps, you should be able to resolve the error.