Not familiar with Unreal modding or development, but that looks like something the devs have failed to handle rather than user error. First steps are verify the game cache in Steam to make sure you aren't actually missing any files, then reboot/update graphics drivers/reinstall game to make sure it's not something simple.
The system requirements on Steam say it only requires DirectX 10, not 10.1 or 11. Of course it's possible the devs don't actually know and have given you the wrong information, which is even likely if they're inexperienced. It does line up with something about your system being different from their test machines -- do you have a 32-bit processor or OS or something? Perhaps integrated graphics instead of a GPU? Also, if you find a redistributables folder with the game, it might come with an installer for the exact version of DirectX the game requires.
Welp... I tried but it seemed like too much of a hassle, so I just refunded them so I could get back some money. It doesn't matter too much thought as what I still have includes:I searched that file name and found this ark thread. They claim that your graphic card doesn't support dx11 https://steamcommunity.com/app/346110/discussions/0/615086038661092696/
also try updating your grapic card's driver
there is also another link about dx11 emulator but i didn't click it. I'm a bit paranoid when it comes to clicking unknown website (it seems to be a PUBG fans website judging from the link)
Bioshock (and the remastered edition)
Devil May Cry 4 Special Edition
DmC Devil May Cry
Dust an Elysian Tale
The Escapist 1 and 2
Fallout 1, 2, tactics, 3 and new Vegas
Danmachi Infinite Combate
Lego Indiana Jones 2
Master levels DOOM 2
Skul: The Hero Slayer
Sonic adventure DX
Star Wars Empire at War
Star Wars dark forces/Jedi knight series
Star Wars Knight of the Old Republic
The ultimate Doom
Ultimate Marvel vs Capcom 3
and I even just got the entropy zero mod.
Thanks for trying anyway @Deliberate Zero and @erobotan.