Good morning Mola,
I'm not entirely sure why you are prompted for a subscription key. There are some possible reasons for that, however you should not have run into any of those scenarios.
I'm with NikK and Simon here, the best cause of action is to reset and start over.
1. Uninstall Internet Security.
- VMS uninstallation tool and our uninstallation tool may be used, as Simon and NikK suggested
2. Login to your SAFE portal (mysafe.f-secure.com) from the computer you want to install
3. Check the list for the problematic computer
- If it is in there, remove it
4. Click "Install" next to Internet Security
5. Name your device and download the Installer offered by the portal
6. Run the installer and follow the instructions
Could you please let us know how it went?