Assuming that you are connected to the Internet when entering your email address and serial number.
If MMM 2016 was installed on Windows 7 or 8 and you then upgraded to Windows 10, then you need to re-install using this procedure.
Otherwise we need more information - see this post.
HTH
John EB
What should I do?
Im using a dell inspirion, my outlook account is always connected too, I closed all running apps, but I believe avg is running in the background and some other procceses in the background also.