Activate Windows 8 Pro

i bought my pc from a friend and i got it updated to 8 pro .. now i am having a problem with activating windows ..

I thought it could be not a legitimate version or the product key exceeded the unlock number so i wanted to buy a new product key and whenever i want to do that i couldn't an error pops up

the error is
0x8007232B

DNS name does not exist


so i want to know what's really wrong and i want to fix it .....

Activate Windows 8 Pro