In the Tails of Fail thread, I mentioned about my PS Plus renewal going slightly wrong. Basically, none of the free games on the PS4 worked any more.

I found out (by digging around the Settings) that I had to renew the licenses for the games manually.

So, if this happens to you this is where you have to look

Settings>PSN>Restore Licenses - use the Restore button to reactivate your free software.

Why this is not automatic, I'll never know.

Well with iOS if you have to restore purchases you need to enter your password again. I think that it becomes a security feature and also some people might not want to restore their free purchases again.