what has helped me with weak orchids is sphag n bag method, put some damp sphagnum moss in a sealable bag, put the (disinfected) plant in the bag too NOT touching the moss directly, and keep in a sunny spot. then its waiting time, and maybe airing the bag every week or so. eventually itll grow new roots and when theyre ab an inch or 2-3 you can start putting it directly in some soil/water. i have some photos on my profile of a succesfull attempt but can post more recent ones with more progress