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.