Have you created an account with DxO? I think that when you go to activate the software, you need to have an active account with DxO. First you go to your account and enter your license info, then you can activate the Nik Collection at the splash screen. I was getting an error message telling me that I needed to check the activation code or check my internet connection when I clicked on the Activate button at the splash screen. Then I went to my DxO account, entered the info and I was able to activate successfully.
Maybe this will help? I hope.
kirk