You need to either need to update or install Ubisoft Connect, then it will stop asking for a key activation.

I have ubisoft installed..and it is updated.

Originally posted by zeko8481:

I bought Far Cry 3 yesterday and I was logged in to Ubisoft... and I download Far Cry 3, start it, and now it's asking me for the key to activate it in Ubisoft, please help me, how to solve it

If you bought Far Cry 3 on Steam, the activation key is already included. Open Steam → Library → Far Cry 3 → Manage → CD Keys and copy the key, then paste it into Ubisoft Connect when prompted. After activation, the game will link to your Ubisoft account and won’t ask again.