Please open your Aion directory, hold down Shift and then right click inside the folder. Click the option "Open command prompt here" and then type "Beyond Aion.bat" ENG.
If it doesn't start the client, there should be an error message which you can post here.
I solved it, for some reason command prompt didnt open, it was a problem on my part, I fixed command prompt by Going to HKEY_CURRENT_USER\Software\Microsoft\Command Processor\ or HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor\
Clicking the Command Processor
and deleting the AUTORUN key
now it works