There have been some issues with nightly updates in the last few days.
The first reason was that I botched a disk array update which was needed as the old ones couldn't cope with the workload, and it had some lagging effects with the update jobs not firing.
Recently I found a second issue - WarGaming have slightly changed the URLs used to search for user data in 0.8.6, and NoobMeter was still using old ones, therefore not getting data updates from WarGaming properly.
I've fixed this issue now, and restarted the data update manually, so it should work now.
The remaining issue is, of course, the artillery reshuffle for which I have to update the parameters in the database. I expect it will take a bit of time to iron out all the issues (though of course that applies to all ratings, not just Performance Rating).
In any case, thanks to everyone who is supporting NoobMeter, whether by donations or by reporting problems so they can be fixed.