Can't launch Mass Effect 3 (Steam version)

Hey, I can't really get any help from EA help, so this is kind of just a question for someone who knows what they're doing.

I cannot launch Mass Effect 3 (purchased from Steam) at all. The main reason why I want to continue playing Mass Effect 3 (instead of LE) is for the multiplayer. I owned it already on Origin/EA app, but I went ahead and bought a Steam copy for achievements and collection sake, but when I try to launch from steam, the EA app just flickers and closes, followed by a "Failed to launch game" error, with a description saying that "An error on our end caused the launch to fail. Try again a little later."  I have tried many things to try and resolve this, like uninstalling EA app, Steam, and Mass Effect 3 with revo uninstaller and doing clean installs, trying to run everything in administrator, and deleting the 71183.dlf file in the License folder in programdata.

One thing that I have discovered is that if I install my old Origin-purchased copy of Mass Effect 3, then I am able to launch that from the EA app just fine. For whatever reason, it seems to be the Steam copy that has this issue. I suppose I could try to refund the Steam copy and just keep using the EA app, but I'd rather have the Steam-related stuff available like the guides and community tab and achievements and such.

Could my issue be something to do with EA app getting confused about how I have two Mass Effect 3s? If so, how do I fix it?