Did you download this through the steam client or aeria ignite client?
I would tell you to redownload steam_api.dll and then go to run and use the Regsvr32 commands to register the steam_api.dll or you could uninstall the game, disable steam temporarily, then redownload the game through the aeria ignite client. The dll should be in the main aeriagames/ava folder and not a subfolder. You can check to see if it still exists there, if so then you can use Regsvr32 commands to register it again or if not you will need to redownload steam_api.dll and register it manually or you could redownload the entire client from aeria ignite and hope it resolves the issue.
Om nom nom nom!
"You want me to give up? I've never learned how to. You do it first so that I know what it is, then I might consider it."