Acer asper tc-780 can not activate windows 10

I bought a asper tc-780 where with embed windows 10 today. But after finishing all the set up, I found the windows is no activated. It says "the product key already been used on a different device" with a err code:0xC004C008. However, the product key should be embeded in the system and is visiable to me. What was happened? Should I make a refund.