Nano Antivirus does not offer "lifetime free keys" or "giveaways" outside of official promotions (e.g., Beta testing). If a website offers a "daily updated key list," you are almost certainly looking at a scam.
You bought a key, but Nano Antivirus says it is invalid. Try these fixes: Nano Antivirus Licence Activation Key
These are codes generated by software pirates. They come in three types: Nano Antivirus does not offer "lifetime free keys"