Question about Poisoner and Mayor interaction

Just played our first two games of clock tower and had an ABSOLUTE BLAST

I do have a really important question regarding the mayor though, here’s the context:

Playing trouble brewing, it is the final 4 players, 2 good team, one was a investigator the other was the mayor and then 2 evil guys, myself as the Imp and my partner as the Poisoner. Going into that night, I tell the poisoner to poison the mayor and then I kill the investigator leaving it a 2v1, all ghost votes still in play. We play along with the mayor and convince everyone to make not nomination so it seems that the good team will win automatically. No nomination happens and then the game master (it’s his first time also) concludes that the Good guys win…..

Shouldn’t the poison on the Mayor have caused his ability not to work and thus the evil team would win? Again, first time players so just seeking clarity on that interaction.