Answer :
The articles had a lot of weaknesses. Their was no executive branch, which means their was no one to actually enforce the laws. Their was no judicial branch, so there was no one to settle disputes between states. Also, the federal/central government didn't have the power to tax. This lead to shay's rebellion because the state's taxes were too high and the federal government couldn't keep them in check.
The Articles of Confederation was discarded because problems arrived from the National and State governments. States did not have a high level of cooperation that they needed to succeed as a nation. There was no National Government powerful enough to wage war against another country or Native Americans. No executive branch or national courts. They needed a more strong and unified government so they met for the constitutional convention and drafted the constitution we know today.