Final answer:
To correct the market share loss in Charlie's retail store, a marketing problem needs to be addressed.
Step-by-step explanation:
To address the market share loss in Charlie's retail store, the type of problem that needs to be addressed is a marketing problem. A marketing problem focuses on identifying and solving issues related to promoting and selling a product or service. In this case, Charlie needs to analyze and understand why his store is losing market share and develop strategies to regain and increase the customer base.