What were three problems of decentralized power under the Articles of Confederation?

Monetary/Fiscal

Laws

Army

Under the Articles of the Confederation, the nation could not mint a single currency, so every state had a different one. Each state could raise tariffs on imports from other states (which doesn't encourage trading between states). You couldn't use money from New York in Delaware, nor in Massachusetts. Also, Congress could not tax the states.

For a law to pass it had to be unanimous. Every single one of the thirteen states had to agree to a bill for it to pass. You can guess that that would hardly ever happen. The bicameral house was instituted for a reason.

The Congress, under the Articles, could not raise an army. That is a problem without need of explanation.