Success? How can success be classified? Is success dealing with every single problem, acting unbiased, and trying to preserve World peace? If that is the criteria, then for sure, the League has fallen since the beginning. .
The aim of the League of Nations was to solve international problems peacefully, improve social conditions, and to ensure justice is done. The leading powers of the League of Nations were France, Great Britain, Japan and Italy. Especially Britain and France saw the League as a great tool to practice their own wants, and their biased foreign policy, however, that was totally against the "idea" of the league.
Leading powers of the League did not want to use their power to solve problems and to find answers to questions, which occupied the world news. France, for example did not want to send troops to the other side of the world, to solve a problem, which was nothing to do with them. That was because of the "potential" German threat. The French primarily saw the League as a tool, which could help protect France from any future German attack. .
Moreover, there were absent powers in the League. America and Russia, decided not to join the league, and that was the keystone. America's main reason for that was isolationism. They did not want to involve in European and World affairs. There was lack of authority in the league. Britain and France did not want to disturb their "future" allies against Germany: Italy and Japan. Japan's invasion of Manchuria and Italy's invasion of Abyssinia was the last reason for the failure of the league, because there was nothing that the League could do because of the policies of strong European powers. Moreover, the league came to conclusions to slow. It took the league about one year to prepare and give in a report for the Manchuria crisis. .
There was lack of armed forces. The league did not have an army of its own. Leading powers of the league did not want to send troops to solve other nations" problems, when they had their own, and when there was a potential German threat.