I have checked the serial number and verified it activates and I have added an additional activation.
 
Here is what I'd like the customer to do:
 
1. Start the software
2. Choose the default option "I have received a serial number and have internet connection"
3. Enter the serial number: 
4. Hit Next

At this point an error will come up, We need to know this error.  For example, "network reply is incorrect" or "security driver missing" are a few examples. After the customer hits okay to this error then the error "no more keys 10006" will appear.  

Basically we always need to know the error that comes up immediately after they enter the serial number. When an error appears a license activation is used, so if they keep getting an error and hitting 'okay' then yes the error "no more keys 10006" will appears.  

For future reference, if customers complain they get error  "no more keys 10006" and we have already added an activation please find out what error appears immediately after they enter the serial number.