Payment only happens when a block is found and confirmed, and there hasn't been one found yet. In fact, I think Coinotron is the only one consistently finding blocks at the moment because they have the hashing power. vPool hasn't found one in a few days, and D7 got lucky and found one shortly after they brought up their server, but has lacked since.

PPC's mining difficulty needs to be re-adjusted and it's happening gradually. We should find a block here in the next couple of days, and then payments will occur based on the proportions of shares you submitted to find the last block. 

We have over 160k shares submitted thus far and no block. Difficulty is at 230,000 right now, which means it takes about 230,000 shares on average to find a new block. So, we should see a block at around 230,000 (it could take a bit more, theoretically it could take a lot more days, but I'm hoping that's not the case =P )