Honestly i don't remember well, but i think you just have to start training your stamina again at the training ground, it will start the event then, if not try going to train there at different times of day, because i think there is a point where she can only help with the training at the evening, if it still doesn't work just talk with her at different times of day again."go and resume ur training with robin"
In this quest, it shows a heart on Robin's bubble but nothing new is there, anyone know wht to do