The Articles of Confederation was the first constitution for the United States, it was known for being very weak and giving little power to the national government. Most of the power was in the hands of the states and the people.
The government could not tax the states. Under the Articles of Confederation, the national government did not have the power to tax. In order to raise money, they had to outright as the states for money. This made it so they did not have enough money to create post offices, create a military, or pay off war debts, making the country weaker as a whole.
The government could not properly create or enforce laws. Because there was only one weak branch of government, they could not create laws properly. In order to pass a new law, 9 out of 13 of the states had to agree to it. This made it very hard to pass anything, along with the fact all of the states had to agree in order to amend the Articles of Confederation.