i think it might be running in auto and some parts of the pool might be broken.
I've received a dash payout from mph on the 5th and the 8th.
There are a lot of reasons. Pools usually payout from coins mined by others instead of going to an exchange and will
delay payouts if there aren't mined coins available in the wanted currency. If they have to buy them on an exchange
then low trading volume can make exchanging difficult. It's better to stick with highly liquid, easilly tradeable, coins for payouts,
like Dash.
I haven't mined at MPH in a very long time, it was one of the first auto exchange multipools, along with Wafflepool and TradeMyBit.
But yaamp/yiimp changed all that.