Why haven't I recieved the rigorous training quests in maplestory?

I completed the 4 training quests for Grendel, and after you do that your supposed to get the rigorous training quests. I didn’t get them however, and now I don’t know how to go about getting the seal of marbas. I searched what the last regular training session was about, and apparently you were supposed to kill stumps, but Grendel had me kill fairys. How can I fix this?
Thanks for the random answers that in no way at all pertain to my question…