Error in Std Cost estimate - Activity price

Hello

I am having a very peculiar situation. We had made all settings for activity price calculation and already run the cost estimates, etc. Since last day, it is noticed that the activity prices are not getting calculated in the costing run. All settings are in place, still we are wondering why this is happening ? System giving messages like structure not defined or formula is not in the work centre, etc. But these are there we checked.