Short answers, pulled from the story.
Louis Barthou served as the French foreign minister until his death in October 1934. His assassination during a diplomatic tour of Yugoslavia stalled negotiations with Moscow.
Paris signed the pact on the 2nd of May 1935 under the watchful eyes of diplomats from both nations. The agreement went into effect on the 27th of March 1936 after ratifications were exchanged in Moscow.
Britain and Italy viewed the pact with deep suspicion and feared being dragged into war for Soviet benefit. Their approval was required before any action could be taken, which effectively neutralized the alliance's military potential.
Adolf Hitler used the ratification by the French Parliament to claim he felt threatened by the agreement. He cited this justification to remilitarize the Rhineland in 1936.
After 1936, France lost interest in maintaining the alliance with Moscow and Europe realized the pact became a dead letter. The refusal to finalize military cooperation left the treaty ineffective against actual threats.