Why does the aggregate demand and aggregate supply mismatch problem arise?

The problem of aggregate demand and aggregate supply mismatch arise when either aggregate supply is more than aggregate demand, or aggregate demand is more than aggregate supply. This problem is also called as disequilibrium in the market. The disequilibrium arises in the market because the factor of demand is different from the factors of supply. The demand is the quantity demand by the consumer at various price levels. Supply is the quantity of goods supplied by the producer at a price level. The equilibrium is attained at single price level, which equates the demand and supply in the market.

Let's take price as one factor; the price of the good has a negative relationship with its demand and positive relation with its supply. Suppose the price of a goods which was at equilibrium, falls in the market. This fall in prices will increase the demand, but due to asymmetric information or limited factors, supply does not rises, this will cause the aggregate demand and aggregate supply mismatch problem