Sims 3 won't launch after merging Origin accounts

@MarLove6  You're absolutely correct that an account merge can lead to an invalid base game CD key and the problem you're seeing.  I'm not sure why the support rep said you needed to uninstall, unless he replaced your base game key.  (In that case, you'd need to uninstall and reinstall to get the new key in your computer's registry.)

You can try going back to support; hopefully a different rep will recognize the issue.  Please let me know how that goes.  In the interim, I'll ask around if there's something else you'd need to say or do and let you know what I hear.  It might take a day or two though, meaning going through support again is probably going to get faster results.

Hi Puzzle, thank you for the response! I went back to support again and he said he replaced my game files? I restarted everything, still doesn't work. I'm going to try again with the live chat and I'll let you know how that goes. Thanks for the help.

@puzzlezaddict So I was just on the phone with EA for about an hour. I tried asking him multiple times to check the base game key but he said we need to go through other troubleshooting steps. I sent him a msinfo file and a dxdiag. He had me install microsoft visual c++, which didn't work. He now believes some files have been corrupted and sent me an email with steps to run a system file checker tool. Through this, I told him it's not my computer as it worked fine just before merging the accounts, but he said no it is your computer, run the checker, and then contact ea support again if the game does not launch. 

I am getting incredibly frustrated. I understand the support is bad but I have referenced the answers HQ many times and told him how it has been solved for other people, yet continue to be ignored. I will try the system checker tool and see if it does anything. Please let me know if you have found what exactly I am supposed to say and thank you for the help!

@MarLove6  I did flag this but thought that all you'd need to do would be to go back to support.  If you want to not have any more arguments with support reps about your system, it might be worth doing a clean uninstall of Sims 3 and Origin, in addition to the other suggested steps.  It's your call.

Check your Windows system files:

Uninstall and reinstall VC++:

Clean uninstall the game and Origin:

If you still can't get anywhere with support, I will absolutely try to get someone to help with your specific issue.  It's just not always easy to know what to do, especially if the support rep says that everything should be addressed from the account side.

@puzzlezaddict Hi, sorry for the late response. I tried everything you said and I did get some error messages:

PS C:\WINDOWS\system32> DISM.exe /Online /Cleanup-image /Restorehealth

Deployment Image Servicing and Management tool

Version: 10.0.19041.844

Image Version: 10.0.19042.985

[=======                    12.5%                          ]

Error: 1392

The file or directory is corrupted and unreadable.

The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log

PS C:\WINDOWS\system32>

and then for the scannow: 

PS C:\WINDOWS\system32> sfc /scannow

Beginning system scan.  This process will take some time.

Beginning verification phase of system scan.

Verification 5% complete.

Windows Resource Protection could not perform the requested operation.

PS C:\WINDOWS\system32>

I have a pretty crap computer and I'm considering buying a new one fairly soon--I might just repurchase sims 3 on steam. Let me know if this unveils anything!

@MarLove6  The errors themselves wouldn't explain why Sims 3 isn't working, but they could signal other issues that explain the problem.  It's difficult to say without fixing the system errors, as in, the ones that lead to DISM and sfc not working.  If you'd like to do that, let me know, and I'll post instructions.  I'd also like to take a look at a dxdiag.

https://help.ea.com/en/help/pc/how-to-gather-dxdiag-information/

If you're ready to get a new computer instead, it's kind of a moot point though.  And before you rebuy everything on Steam, which is not a bad plan in the grand scheme of things (no mandatory Origin tie-in, no being forced to start the game through the launcher), you may want to install from Origin on the new computer to see whether it works this time around.

@puzzlezaddict Ok I've attached the dxdiag. Yes I would appreciate the instructions, I'll try fixing the system errors. It would probably be a few months so I may as well see if I would be able to play it. I'm going to try support as well once more since I have done I believe every troubleshooting step they have. Once again, thank you for the help!

@puzzlezaddict I tried EA support again and it's fixed!! A support person named Akash helped me out. He replaced my base game and voila, it's working!!

Edit:  I just saw your new post, and that's great to hear.  I still think you'd want to do the following though, given the errors you've seen.

@MarLove6  The easiest way to address these issues is with a repair install.  First, go here:

https://www.microsoft.com/en-us/software-download/windows10

Download the Media Creation Tool, which will allow you to create an ISO of the latest Windows 10 build.  Proceed as if you're going to burn the ISO to disc, but when it's ready, close the MCT instead.  Then right-click on the ISO and select Mount; you'll now see it listed as its own drive in a File Explorer window.

From there, use this tutorial:

https://www.tenforums.com/tutorials/16397-repair-install-windows-10-place-upgrade.html

While this process should allow you to keep all your current user files, it's always best to back up anything essential beforehand, just in case.  If you don't see the prompt asking whether you want to keep personal files and folders (step 13), back out and try again.

@puzzlezaddict Thank you for the instructions! I'll do the repair install now