Error when check for updates - Also, what is current PL7 version?

I don’t know the URL PL is trying to reach but there is at least one more thing you can try, before you go for the nuclear option as suggested by @swmurray

Now that you have the latest version of PL7 installed, re-run the installer. When you do that you should get a dialog that looks like the one in this post:

Choose the repair option. When it completes, reboot and see if that fixes the update error.