Are you trying to activate the latest release 4.1.0?
Only the latest versions of the plugins will activate. I had to reprogram the plugins to a new server location and system. Old plugins are not programmed to the new activation system.
My guess is that you might be trying to activate an older release. Please let me know if that is the case.
If version 4.1.0 won’t activate then please respond here is the forum with a screen shot of the message it gives when you try ton activate it.