Activation Key Problem

I already have an activation key.
But it wa ssaying that the key is invalid.
Please help me to get out of this.

It could be because the activation key is for version 6, and you are using version 7.

Or more likely, the key is activated on another computer. If it is a Free License you can only activate it on one computer at a time. You will need to deactivate it on the other computer before you activate it on a second one.

Or maybe you did not copy the key properly. If you have lost your activation key, or recorded it incorrectly, you can get a copy sent to the registered email address, by going to http://www.emclient.com/lost-activation-key