It's happened to me as well, I've tried a couple different things and a different save files. I just can't figure out what the problem is. Sometimes I'll get a ribbon for a pie in one of my files. I have a whole separate save file for a super sim I've been working on and I have this problem for every single fair on it.
I am having the same issue. I entered a cow and strawberry milk into the fair. I received a first place ribbon for my cow but no notification at all for the strawberry milk. I was given both back into my inventory. This seems like it is a pretty well documented bug at this point.
