This happened to me last week (I think) or something like it. I had to reboot for some reason and after 3 or 4 hours still no PG. Playing around with it (I think) I went in Options and Settings / System Settings / #8 Installer Menu / #1 Installation Wizard and then I think #7 Verify Voom is what may have brought it back. I'm just guessing here. After a few minutes the PG came back. It could have just been coinsidence. Also, I did other things while I was playing around, but this was the last thing. And, something worked. Probably, just coinsidence.