Q.Moon cactus
I got a moon cactus from Walmart, I got it in December and it was red at the top! I placed it in a window seal with the blinds slightly open but soon moved it to the table. The red top turned orange and it started to look very sad. Now it is all shriveled up, thin, and hard. What happened? Is there no hope for it?
Certified GKH Gardening Expert
It sounds like it started suffering from a lack of light, coupled with a bacterial infection. This can happen when it remains too moist for too long, or if the infection was already there when you got it. Sometimes it can take a little while to show. This cactus appears to be too far gone to save. On the next go, I would immediately transplant into a larger pot with cactus mix. This will allow for proper drainage of the soil.
Here is an article that will give you some more information: https://www.gardeningknowhow.com/ornamental/cacti-succulents/moon-cactus/care-of-moon-cactus.htm