Not enough Information

[NedZep]

Many times there is not enough information based on the cards to guess the solution. Is this normal, or am I just stupid?

[Jellby]

Which cards? The criteria cards? Yes, that's normal, they don't give full information.

The verification cards? That should not be possible. If you knew all possible red+green answers, you'd immediately know the solution, because it's the only code that gives green in all verification cards.

Your problem is that you don't know all red+green answers. You only know which condition each card could be checking (one of those listed in the criteria card), and whatever actual tests you do.