What were the reasons European counties were not paying their war debts ?

Their economies had been weakened in the war; they were unable to raise money because U.S. exports were limited by high tariffs; Germany failed to pay them expected reparations.

the mongolian invasion of china and central asia resulted in a disruption of the silk road as the chinese garrisons lost support from the chinese kingdoms which fell under the mongols. however, as the mongols established a formal dynasty in china, the successors of genghis khan restored the garrisons along the silk road allowing the safe travel caravans again.