The starting difficulty is too high for your average beginner. Start with just one interval, then increase. Also, you should let people try a few times rather than just allowing one attempt.

Thanks for the feedback. I've adjusted the Practice Mode so you can turn the starting sequence down to a single note. The "grace note" allowance (see what I did there) for allowing a player to sort of find the right note has been asked for a few times - I'll try to get that implemented later this weekend!