When you receive this error while trying to import your Windows 10 product keys to KMS VAMT server 3.1, the only way is to upgrade your VAMT version.
It is not possible to import Windows 10 keys in VAMT 3.1 keys.
Download the software from Microsoft:
https://msdn.microsoft.com/en-us/windows/hardware/dn913721.aspx
Direct download :
http://go.microsoft.com/fwlink/p/?LinkId=526740
run setup and install SQL Express and VAMT.