I have recovered several Scolymia's that I have purchased for pennies on the dollar over the years. You can see a few feeder tentacles in your photo. It is likely so weak that it will be very difficult for it to grab ahold of anything solid, but you need to have some patience. Feed small pellets, or finely chopped mysid shrimp and shut down all water movement. It may take an hour for it to ingest something, or it may take several days of trying for an hour each time before it eats something. Once it eats I would suggest feeding it every day for several weeks and then back off to every other or every third day. Once it starts eating you'll see improvements weekly.
A couple of other suggestions.... don't feed it phytoplankton at this point. It won't hurt to feed plankton, but it will not promote tissue regrowth IMO. Additionally, I would recommend the removal of the cleaner shrimp. Cleaner shrimp and LPS that are fed doesn't work. The shrimp will eventually kill / minimally destroy the mouth of LPS that you're feeding.