I just got to VIP level 6. Some of my kingdoms went to power level 1 while others didn’t. I don’t mean the ones for which I haven’t completed the quests, I mean ones which I have. For Example, Broken Spire didn’t go to power level 1.
The reason why not all your kingdoms didn’t upgrade is most likely because you might not have any troops in that kingdom to upgrade to level 5 (the troop).
If you open your gold chests, you might upgrade more kingdoms as you acquire more troops.
No, an investigation isn’t necessary anymore. All of my kingdoms are now power level 1. None of my kingdoms were at power level 1 before reaching VIP 6.