Content Paradise has indeed gone offline.

Here's a notice from the Smith Micro Forum website:

On September 2nd, 2019 we will be closing access to Content Paradise, which we shutdown back in September of 2018. If you haven’t done so already, please take the remaining time to login to your Content Paradise account and download any previously purchased items that you want to backup. If you have any issues with gaining access to your account you can contact the Smith Micro support team:

https://support1.smithmicro.com/portal/home

I don't know how relevant that notice still is though.