I have a large parent deck with all my other decks as subdecks within the main deck. This is the deck I use to go through all unsuspended cards at once. I noticed recently that it was not showing all of then new cards in the main deck. It would say “0” but then in the subdecks I could see new cards still that I had not reviewed and were due that day. The only way to see/review these new cards is to go through each subdeck one at a time. This only seems to be occurring with new cards and not review or learn cards.
Probably you have reached your parent deck new cards limit. Try increasing that setting.