I am trying to add a PC to my protection. States expired, but not expired

Hello there, welcome to the Community!
 
It might be possible that you did not get the key code entered in quite exactly right, or perhaps you used an old key code and not your current one. 
 
In the Console,
Click your email address at the upper right
Click Manage Key Codes
Make a note or write down the key code that is shown as active/not expired.
 
On the new computer
Open WSA
Click the gear tool next to My Account
Enter that key code we noted above
Click the Activate button
REBOOT THE COMPUTER.  Before doing anything else, even scanning, reboot the computer right away.  (I know this sounds odd, but once in a rare while if an expired or incorrect key code has been used on the computer, I have in the past seen the new one just plain not correctly save.  This method worked to save the new key code.)
 
Now try to do the scan and let us know what the results are.