Use any of the files linked at your own risk. This guide works as of May 2024 and cannot say how long and whether it will keep working in the future.

Have you returned to play Mass Effect 3 in your Steam Library or purchased this game only for it not launch and ask for a product key that cannot be found like the image below.

EA should really fix this problem that did not exist before and was working fine without users needing to perform such steps, but this is what currently needs to be done. It looks like a migration issue with the link system they have between their new EA app/Origin and Steam activation that was working before but somewhere along the way they broke it.

Exit the current EA app if running, do not need to uninstall it. Download EA Origin program from Here[download.dm.origin.com] or if you already have a version downloaded, does not need to be latest, install it.
How long this link will work for is unknown so keep a backup copy while you can. Use the full setup version that is around 200mb and not the OriginThinSetup.exe as you may run into problems later on.



It should finish installing and the message at the end if logged in should say to use EA App to continue. Just close the box and MAKE SURE to exit the app from taskbar.

Go to this GitHub page[github.com] or this one[github.com] and look for the F__k_off_EA_App. Description - "Keep using Origin instead of EA App"
Read the information about this app. From Releases page download the F__k_off_EA_App_installer.exe file
and run it. (Below) *Pretend EA App is installed - tick this box incase EA App tries interfere later on.

Make sure Origin and also OriginWebHelperService in Task Manager is closed if running or did not close before.


Next after finishing setup, also from the GitHub page download the "version.dll" file


As in the readme copy/move version.dll to C:\Program Files (x86)\Origin or wherever Origin is installed and replace existing file.

===IMPORTANT STEP=== before you run Origin. As per the FAQ in Github link go to your "EACore.ini" file in the Origin install directory and paste the following

[Bootstrap]
EnableUpdating=false



If you do not do this step, may run into the issue of Origin asking to update the program but it won't update and give an error like below.



Finally run Origin.exe and login with details and tick sign in automatically.


and now should be able to see Origin as before.

===ANOTHER IMPORTANT STEP===
To run without any other startup issues of Mass Effect 3. There should be two Mass Effect 3 titles in the library section with the Steam banner, one with the N7 poster.

Right-click on the game and choose "Game Properties"

then in the "General" tab untick "Enable Origin In Game"

Do this for each of the two entries in the Origin game library. If overlay is enabled the game may not successfully launch.

This step will also be shown again further below for the newer EA App to disable the application overlay or the game will show at first trying to start but will not launch successfully.

Press "Play" Mass Effect 3 in your Steam Library and it should now startup after EALink.exe runs for a few seconds in Task Manager.

If it comes in handy for any reason in the future, this measure is working as of September 2023. How long before EA breaks this work around is to be seen for legitimate owners. In Steam not every game allows to view product key and in the new EA App there is no option to view your purchased product key at all.

In Origin, in My Game Library, choose game and right-click on the title and click Game Properties
or click on the game title and click the settings cog icon and click Game Properties
to see your key.


Check all games in your library if wish to, some will have a key some will not.

Now that Mass Effect has managed to be activated and works again, you can keep it as it is. Optionally If would like, Mass Effect 3 can now run through the current new EA app.

First it needs to recreate the original EA/Steam integration and run the game through the new EA app. All that is required is to close Origin/OriginWebHelper, don't need to uninstall, just run the EA app.

Further optionally if desired to uninstall Origin.


If try to run and play Mass Effect 3 now the following error may pop up.




Just launch the new EA App first


Now before hitting "Play" just as before for as the Origin overlay needed to be disabled, the EA app in-game overlay also needs to be disabled or Mass Effect 3 may not launch and startup.

To do disable the in-game overlay for the EA app. Click on the top left corner icon in the EA App window to bring the app menu and click Setttings.



















Next go to the "Application" tab and scroll down to "In-game overlay" Turn the switch
off for "Enable in-game overlay.

Now hit "Play" Mass Effect 3 either through Steam or the EA App and game should launch
successfully.

It will work as it was meant to work as intended in the first place through the current new EA App without running into original launch problem.

Sources and credit
https://github.com/p0358
https://www.youtube.com/watch?v=W-OEkuXkERA
https://answers.ea.com/t5/Origin-Mac-Client-Technical/Download-Latest-Standalone-Setup-For-Origin-Here/m-p/7897772

Thanks to the above. I have complied some of the steps from above needed to resolve and fix this Mass Effect 3 Steam startup problem created by EA, if it can help any other user. How long this will still work remains to be seen but for now enjoy Mass Effect 3 again and saving the galaxy.