I've been reading JN's post about this, and it seems that some users aren't receiving anything at all, no NP for level completion, no items. Like me. I'm going to guess it's a possible glitch, or it's because the site has really horrible lag and the items/NP are having a hard time getting through.
For those of who you who can play it:
3 stars gives you 1k
2 stars gives you 600NP
and I'm not sure what 1 star gives you.
Based on progression though, I'd say possibly 200NP. Since 600NP is 400NP lower than 1k.
If you miss getting 3 stars, redo the level. Once you hit 3 stars you'll get the 1k.