If you run the game and see:
Failed to load
Terminal error at stage: HEADER
As a test, can you please try editing the file 'Eldevin.l4j.ini'.
For the Steam version on 32-bit Windows it is located by default in the '\Program Files (x86)\Steam\SteamApps\common\Eldevin' directory.
For the Steam version on 64-bit Windows it is located by default in '\Program Files (x86)\Steam\SteamApps\common\Eldevin'
For the client downloaded from Eldevin.com it can be found in the directory you installed the game too.
The file should currently look like this:
# Eldevin runtime config
-Xmx1024M
-Djava.library.path="native"
Try adding the following line to the bottom of the file then save and close it:
-Djava.net.preferIPv4Stack=true
Next try running 'Eldevin.exe' in the same directly and see if that works for you 
Regards,
Andrew