Is that succulent soil?
TatumRiley said:
Is that succulent soil?
I added sand when I repotted it 
Jem said:
What kind of substrate is that? It looks like play sand! Probably not ideal. You could try propagating it, but it’s not easy. The brown parts won’t recover, though.
It’s a mix of sand and succulent soil. I might need to get proper soil for my other plants.
I had a similar issue. I used a grow light, repotted with better soil (nothing too fine), and gently cleaned off the roots before replanting it at the same depth. I misted it weekly until it turned green again, then switched to watering lightly once a month. It’s thriving now!
Organic succulent soil works best, no sand. 
Looks like there might be root rot. The bottom part seems done for, but you might save the plant on top if you cut it off, let it dry and callous over, and then replant it in fresh cactus soil.
What nutrients are you giving it?
TatumRiley said:
What nutrients are you giving it?
Does water count? 