Getting invalid serial key while installing Nero 10 Multimedia Suite Platinum

I am with windows 7 operating system and as after the release of nero 11 I just made a removal of the nero 10 version. But after some time I received some issues with the nero 11 setup and was intended to return to the previous version i.e 10 version. But after I was with inserting of the serial key it claims that my serial number is invalid, can you give me some suggestions regarding the same.

I want to ask some questions regarding this case and would tell you that did you make use of your copy of version 10 as the basis for a reduction in the price of version 11? And if you have tried this one you're version 10 serial number will be invalid. So I would tell you that you are able to still make use of v10 on the first machine if you didn't uninstall it.

I also had the similar issue and to tell you regarding the same,I would further add that when you got into the installation on the subsequent machine , it should tend to inquire you why you're making attempts to install it on the second machine. It does that since because of the EULA.

My issue was solved, after I turned my Antivirus and just did my Firewall to off mode and it accepted serial and started to install. I just wonder how the Antivirus can solve the issue of the serial key mode. Can you predict what could be the exact reason behind this .