this happened twice already was running this morning now when i got home it is off why is it shutting down?

Normally a server shut down happens due to one of three issues:

1. The server crashed, and failed to restart.
2. The server was stopped by an Admin.
3. The server had an update, and due to a failure in the update process, boot looped and then stopped.
4. You have a "malicious" player who has somehow found your RCON port and password and forced a shutdown.

I would check your server charts to see what's going on there. And if you're not able to see a reason for the crash, and your account logs to make sure no one was stopping the server. 

Barring that, I would submit an email ticket.

server are still shutting off gonna rebuild it i guess becuase it's not making any since this time it's cutting off when i try to join saying Server was stopped 10 minutes ago because it exceeded 12GB RAM first off my mods are 22 mods installed totaling 3,790MB none of which goes past 670 mb in size no major dino over haul mods server is been wiped so no buildings nor tames, only dino mods are Ark Bionic which is only 417 mb and human npcs 53 mb and settings are very low for both no one else really plays i mainly use my server for making build designs the rest are either for taming or build mods so i'm at complete lost on why my server keeps shutting down , espcially considering i really haven't been playing last few days

From the FAQ on the Discord regarding ram usage:

2) Your Memory Usage has exceeded the 12 GB cap for a 60 slot, or the physical limits of the machine for a 250 slot server.
The common causes of that is:
a) Check your mods. 99% of the time, RAM getting capped is because you have WAAAY too many things trying to be active at once, and you've just overloaded the server.

b) SFTP into your server and check your map file size. The game has to load the whole map into memory, and if you're using a mod that continually adds to the map file (Such as Awesome Teleporters) it is possible you will cause your map to eventually not be loadable.

the primal NPC's build their own bases and tame their own dinosaurs, they also plant their own turret plants on top of their bases, it could be possible they built waaaay too many bases with the turret plants. Try removing that mod, or try a wild dino wipe.

Yep. Primal NPC mod is amazing, but if your player base doesn't go out of there way to keep them in check, they will take over your server to where the humans can't play any more.

Keep in mind, each NPC from Primal NPCs can and will do all the same actions that a normal human will do on your server. So a 60 slot server with 25 players and 45 NPCs on it is using upwards to the same resources as 70 players*.

* The caveat here is those NPCs arent' active when not in render range, but boy howdy if you get them all hopping.

i don't use primal npc never will it's buggier than 2 dollar ho .. human npcs not primal

also ..45 NPCs on it is using upwards to the same resources as 70 players*. ????? i mean how are they any different than dino running about the human npc mod yeah some  tiny buildings are made but they don't tame dinos they just mainly walk around and sometimes attack things that attack them

Primal NPCs build structure, are a moving resource scanning AI, and "extend" the render range of players within their owner ship bubble. Primal NPCs also spawn tamed dinos alongside them, and those dinos are treated as "tamed" dinos. You can't knock them out, you can't tame them, and they do have a food stat. (Even though they don't get fed, you can technically starve them to death.)