Is it normal for some my teeth to not properly fit on the Invisalign tray?

So this is my first tray and it's been 6 days, but I've notices that the top tray for one of my teeth pops out a little, as in it doesn't go on top of my teeth like the others do. Basically there's a little gap in between the top of the tooth and the edge of the tray. However, the button for that teeth fits perfectly in the pocket. Also for the bottom tray there's the same problem for a few of the teeth in the back.