It can also take a while for a rating to go through. Once you tap the allotted stars you'd like to rate an app, you need to wait until you see the "Your feedback was submitted" modal to appear.

Not exactly a day later but the ratings tend to come with 6 to 12 hours delay. Sometimes more.

Also, there's this strange thing that some of the ratings disappear and come back later or not.

Ah that makes sense. I wasn't aware of that.