This particular mission (Season 1, Missino 6. "Moshi University") is bugged for Katsuma players only. So if you have a Katsuma as your initial sign-up monster, you will not be able to progress through this mission (This is ONLY for Katsuma players, other monsters shouldn't have issues).

This may mean that you think you won't be able to obtain Penny the Mini Money. However, there is a seed combo for them if you are unable to progress through the mission.