Collective Security 1930s

Why did collective security faild to keep peace between 1920 and 1935?
Collective security was an idea that peace could be preserved by acting together, to prevent one country attacking another. This idea failed between 1920 and 1935 due to the depression, The Manchuran dispute, and The Abyssinian crisis. collective security had a permanent court of international justice, arbitration, an investigation system, and economic sanctions. In the covenant of the leage of nations it was said that member states should refer their disputes to any of the previews mentioned.
The depression was an economic failure. The wall street crash in 1929lead to economic , social, and political problems. These social, economic, and political problems lead to