The soil looks completely wrong for a succulent. Wiggle your finger down into the soil as far as you can reach and tell us how wet/dry it is. If the soil is damp, don't water. If its dry do water, but water until some comes out the bottom of the pot.
The plant has never gotten enough light so probably has a small rootball. Giving it adequte light now will not fix the problems it already has.
If the soil is wet, and has stayed consistently too wet, combined with low light, it may not have any viable roots. Of course, the same thing can happen if the soil has been kept too dry but considering the soil, I'm guessing too wet.
I'm not sure what you should do at this point except hope it gets better. I don't think the plant has enough stored reserve to reroot.