I keep getting the message, 'There aren't enough supplies to satisfy the demand', but I'm sure I've bought enough.

•  You may have put a new recipe on your menu, causing a need for ingredients not yet bought.
  
• Demand changes frequently. There may be a new trend causing greater demand for a certain ingredient. Check the demand value in your menu for each pizza selected and look at what each Pizza needs.
  
• Supplies may be rotten, so would have been thrown in the garbage. So check on the quality of each ingredient.