It looks like a habitat-collected plant. This means you have two problems: (1) it has yet to get used to growing in a container and (2) it has to adjust to growing in a container while also growing indoors.

I recommend unpotting it, taking photos and posting them here. I can not suggest watering it more often because if it already has a problem under the substrate, that will make it worse.

Pachypodiums are very, very, very slow growers. They are slow to respond but deteriorate fast when they cross a threshold. The good news is that it isn't impossible to rescue a troubled one, if you catch it early enough.

Let's just find out what we're dealing with first.

(p.s. it would help if you can narrow down your USDA growing zone and whether you have an outdoor space you can move this to later)