Question is pretty much as stated in the subject line, but if you want me to elaborate: I have been trying to play ARK with friends, though it seems choosing a time immediately post-expansion update was very unwise. We formerly used Nitrado with no trouble, but couldn't get our Valguero server to load our mods. Then I found this service and thought it quite promising, but encountered the same issue. Admittedly, we run over forty mods--including S+ and StructureSaverr2--but these have been working flawlessly for me in singleplayer across multiple ARKs.

Plainly, the problem wasn't Nitrado and isn't ARKServers.io, but the game itself. My personal games work great, though. What is different about servers? Why do some mods break servers, but work perfectly in singleplayer?

Please note this is not a complaint post, because I know full well that Genesis broke everything. I also know Wildcard is famously slow to address breakages they cause. This is more intended for educational and conversational purposes! That said, my crew will surely be playing here when the devs sort their darn game. :3

.> omg, no edit function for my malfunctioning keyboard errors....

Short Answer: ARK started with pretty piss poor server code.

Long asnwer: The Alpha for ARK initially tried to run servers at a 60 fps update rate. This was current at the time for most first person shooters, but it failed miserably, so when the beta came out, it was dropped to a 30 fps codebase. Stability was better, so the Early Access also used the 30 FPS base, which means the servers at launch became hard coded to try and update at a maximum of 30 fps.

For a server, this means every second, the server tries to update across all clients 30 times, not that a graphic is refreshed a maximum of 30 times per second. Most first person shooter games, for comparison we'll use Unreal Tournament as it's made by the same company, updates the server at a minimum of 60 fps. In a game that people are locally running at 80-120 fps this is disastrous, as your computer can be doing 4 things in the amount of time it takes the server to "sync" once.

This, by itself, wouldn't be an issue. But the mod system derived from the base code is generally utilized by hobbyists. I mean no disrespect to those modders who deserve respect, because they absolutely deserve it (Blitz, TC, Pikkon, etc.) but the average modder who makes a mod and ships it out to Steam is an ignorant.

Not dumb, but simply ignorant. They start by building their mod for single player, then afterwards retro fit multiplayer onto it. This causes all sorts of sync issues, as that methodology normally involves testing something, getting a report that it's broke in multiplayer, and then patching the symptoms, not the causes of why it's not working.

So often times, when a amateur's mod works due to a hack job on version X.X.X.Y, it folds pretty hard on version X.Y.X.Z because whatever sub system (Read: Not Core) ARK Tweaked doesn't work with their hack job, because WildCard actually updates their program with the expectation that modders are following the style guides and programming structures as built, and not simply by "This worked, cool! I don't know why, but fuck it, let's move on."

Hope that sorta helps answer your question?