Words never appear in "Due for Review"

I have added words to my vocabulary list and I have waited two days but nothing is appearing in “Due for Review”. Is this a bug?

I just joined this site a week ago and I think it took until day 4 for my words to start showing up in Due for Review section. Maybe day 5? I was reviewing lessons as I completed them, so was thinking that had something to do with it.

Please take a look at the help article with an explanation on how the SRS system works: