During the Bount arc Rukia tells Maki she can not use her zanpakto. Why is this? All of her powers should have returned to her.
So there's two things that may be contributing to this:
- Shinigami cannot wield their Zanpakuto while using a Gigai.
Gigai are artificial bodies which Shinigami can inhabit to blend in with humans in the human world or to restore lost spiritual power. While using a Gigai a Shinigami's powers are drastically reduced to help ward off hollows and make blending in easier. To the best of my knowledge Shinigami are always shown to need to exit their Gigai (or in Ichigo's case, his physical body) to equip their Zanpakuto. While in a Gigai Shinigami are capable of Hado which is decent for self-defense but for anything more intensive they need to leave their Gigai and use their spirit form. This is relevant since Rukia does draw her Zanpakuto during this arc but only after being forced out of her Gigai by a Bount while under mind control. This implies she could have drawn her Zanpakuto against Maki but for some reason chose not to. The reason she chose not to may be a feeling it wasn't needed or it may have to do with the second thing, she's still recovering.
- Rukia's soul is still damaged due to Aizen ripping the Hogyoku out of her soul at the end of the previous arc, Soul Society.
Later on in the arc, Rangiku says that Hisagi told her that Rukia's soul was damaged before and that her soul takes longer to heal than her body. This may be referring to the events of this arc but given Rangiku and Hisagi (who haven't seen Rukia in a while) seem to know about it it seems likely this soul damage is leftover from something prior and Rukia has explicitly had her soul damaged rather recently when Aizen tore the Hogyoku out of her. This could imply that Rukia was ordered to stay in her Gigai to heal and while she could take on her Shinigami form (as she does while mind controlled) it would hamper her recovery.
Note: I've never watched the Bounts arc (I've only read the manga and Bounts was anime-only). I'm using the wiki as a primary source which has citations but those citations reference episodes which I can't verify without watching so I may not have the whole picture.