Since you've come to the emergency forum, we know you want a fast answer to your question. In order for us to figure out the problem as quickly as possible, we ask that you answer the following questions as best you can. Some of them may seem odd, but they're all designed to give us the information we need to give you a good solution for your problem. The things in the [ brackets ] are there to make this post easier to read once submitted. Thanks!
1. What kind of substrate is used in your tank and how deep is it? Coconut, grey-brown
2. Do you have gauges in the tank to measure temperature and humidity? If so, where are they located and what temperature and humidity do they usually read? Yes, they are sto the side and usually read between 75~87°F
3. Is a heat source used in the tank? If so, what? Bulb, black/night light
4. What types of water are available (fresh or salt) and how is the water treated (what brands of dechlorinator or salt mix and what ratio is used to mix it)? fresh and salt watet, it's bought ready to use
5. What kinds of food do you feed and how often is it replaced? I have been feeding him fruit because he refuses to eat anything else, and am trying a new food that he too isn't eating
6. How long have you had the crab and what species is it, if known? I've had him for almost two months
7. Has your crab molted, and how long ago did it happen? I BELIEVE he molted two weeks ago; I didn't bother him during just in case and only replaced food and water
8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing? it's a clear tank, ten gallons, and a "grate" lid
9. How many crabs are in the tank and about how large are they? There is one, he's about three inches
10. How many extra shells are usually kept in the tank, if any? three
11. Have there been any fumes or chemicals near the crabitat recently? No
12. How often do you clean the tank and how? I "clean" the tank every few days by scooping around the "sand" and misting it. But I change the water every other day unless I see hom bathing in it and change the food daily.
13. Are sponges used in the water dish? If so, how are they cleaned? No
14. Has anything new been added to your crabitat recently? Just new type of food
15. Is there any other information you would like to share that might be helpful (anything that is regularly part of your crab care, playtime, bathing, etc.)? I "play" with him every few days unless I can tell he's scared or stressed
16. Please describe the emergency situation in detail. He isn't moving. He was fine yesterday, then I slept 18 hours (long story) and woke up and he was sitting in his water dish (it's not too deep and that's normal for him) but I moved him because I was gonna change the water since I didn't get to yesterday or day before because I was in the ER all night into the afternoon next day (my nephew put him new food, I video called, it was his regular food) so he ate, but now he's not responding. He won't move or anything, when I pick him up he's limp and he usually comes out to climb on me or he goes in his shell, but nothing. He's been in the same position with his feet out for hours. I can add anymore info I forgot, I'm jus panicking so maybe I forgot something.

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UPDATE: I called the VET ER around here (I hadn't known they helped with hermit crabs) and they told me the things I and anyone else already knows, but they also suggested drawing a circle around him to see if he moves any within 24 hours. She said if not then it's "safe" to assume he's passed away but I'm gonna also wait for the smell as well like the pinned post said here.
He hasn't moved, I believe. I THOUGHT I saw him twitch a couple times, but it could have also been me hallucinating (I am schizophrenic. So I have no way of knowing if that happened or if that was a hallucination).