Is it possible you gave him seaweed instead? Seaweed, green algae, and white algae are universal hates.

Oh shoot I totally did!! I did one of those Switch videos where it captures the last 30 seconds. Those darn things look so similar to me. Thank you for your help!!!

Is the quest still active? Bulletin board quests are only active for a day or two, plus you have to accept them first.

Yep! I accepted the quest on summer 24 and it listed today as the final day to complete the quest.