Hi,
Do you use a test account with the "debug" mode activated ?
If you didn't specify the access key, at this moment the document could be considered as invalid because a information is missing. The UPS message said that the XML is valid but the document not. It means that some data are missing.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.