Don't forget about the fortune teller (checking relationships and treasures) and the bartender (important quests).
It is possible that you forgot to complete an important story quest or you forgot to pay attention to one of Celica's friends.
In my case, progress began after I allowed Celica to trust Nel during meditation. Before this, Celica tried unsuccessfully for at least 2 weeks, she even talked about it.
Celica had the maximum level and developed all the basic skills.