Producers, like the Tool Barrel, go into a cooldown period after being emptied. During this time, they can't produce items. After the cooldown is over, they will be refilled and be able to create items again. 

 

A producer that is on cooldown will display a clock icon at the top right corner, indicating how long it will take for the producer to replenish. Selecting the producer will show the exact time required for the cooldown to be over.

 

For most producers, Gems can be used to speed up and skip the cooldown.