Auto MRP run in Re order based planning

Hi,

Let me explain a scenerio: MRP type is VB for certain materials (spare parts). So previously when the stock falls below the re order point, the system automatically generates planned orders. But for the last few days, I am finding that, evenif the stock is below the re order point, MRP run does not takes place automatically. It is to be mentioned here that a variant for MRP run is created by which MRP run has to take place automatically with generation of planned orders (tcode MDBT)

Please advice me as to how can I get my previous situation back? (Previous situation was auto MRP run and generation of planned orders when stock falls below re order point)