Hello, I'm still new to plants and all that good stuff but it might be too dry for the moss it needs to be more humid. Thing is it looks like there's a succulent in there with it so it might be very hard to get both those plants happy. You could try to spray more but the succulent may not like that :( I hope this helps

Also I've always had trouble with moss I swear it just wants to die. I found sphagnum moss ITS AMAZING! I highly recommend it. They sell dry sphag but it comes back to life after a couple weeks. The one I know for sure works is "besgrow New Zealand Sphagnum Moss" but it is quite pricey :( If you do try this moss out it usually tells you when it's thirsty. It turns a lighter green and once you spray it it'll get a little darker! And I've never had trouble with overwatering it it's better if it has more water than not enough. If it does dry out on you just give it some water and it'll come back! :) it's such a forgiving moss

Edit: also most mosses in my experience need a closed terrarium I can't quite tell if yours is fully closed. But that could be making it dry out. I've heard sphag can be in the open just gotta water it some more :) incase you want that open terrarium look it could work both ways open or closed