Could you post a photo showing where the plant meets the soil? It may be planted too deep.

What planting medium did you use?

Thanks for the reply.
I've just repotted it and the roots are about half way down I reckon. They were quite long and fiddly so I had to move them about!
It was originally in cactus soil and I have just repotted it into cactus soil again.
Here is another pic

It would do better in a less organic mix, in my opinion. Also I would plant in unglazed terra cotta, so the soil can dry out faster. In any case, do not water again until you see improvement, and some active growth. Good luck.

Christopher