There are at least two ways to read this question.
First, it could be asking us what events showed that the Articles of Confederation were a failure. One answer is that numerous trade disputes between states showed that the Articles were a failure. The various states acted more like independent countries than like parts of the same country, trying to hinder trade across state lines. This reduced the size and the potential of the US economy. Another event was when Congress tried to impose a tariff in 1781. This was supposed to help stem the flow of British imports and help American producers. It was also supposed to pressure the British to stop restricting American trade with British colonies in the West Indies. However, the Congress had to ask the states for permission to do this and the states had to vote unanimously to allow it. One state (Rhode Island) refused permission and the tariff could not be implemented. Finally, there was Shays’ Rebellion. This was mainly a state matter, but when Massachusetts asked Congress for help, Congress had no legal power to help and no way to fund any action that it could take. All of these things show that the Articles were a failure.
Second, this question might be asking what caused the Articles to fail. The answer is that they failed because they gave too much power to the states and not enough to the national government. The Articles were set up in this way because Americans wanted a government that would be unlike that of England. They did not want a strong central government that could tyrannize them. However, they went too far and created a national government that barely existed. The national government could not force the states to do anything. It could not even levy taxes to support a military. Instead, it had to ask the states for money, something that the states were rarely willing to provide. The federal government could not stop states from setting up trade barriers against one another and it could not stop them from making their own policies with respect to foreign trade. The Articles of Confederation set up a very loose union of states that were practically independent countries. Because it did this, it failed to create a strong, unified country.