Re: The sims 4 64 bit won't load due to missing core/activation64.dll

@leoetralip  Just to be sure, you're seeing exactly the same error as is in the thread title?  If not, please post a screenshot of the error.

Either way, please also run a couple of basic checks of your Windows system files.  Here's how:

• Hit Windows key-X
• Choose either “PowerShell (Administrator)” or “Windows Terminal (Administrator),” whichever option is offered
• Inside the window that appears, copy and paste “DISM.exe /Online /Cleanup-image /Restorehealth” without quotes, and enter
• The system will start validating soon. If it throws an error, please list it here
• After it reaches 100%, hit Windows key-X again
• Again, choose “PowerShell (Administrator)” or “Windows Terminal (Administrator)”
• Inside the window, copy and paste “sfc /scannow” without quotes, and enter
• Post the message you receive here

Restart your computer, hit Windows key-i, select Update & Security, and click the box to check for updates.  If any install, restart again afterwards.

Clear the EA App's cache:

https://help.ea.com/en-us/help/faq/clear-cache-to-fix-problems-with-your-games/

Then uninstall the App, restart your computer, download a fresh copy of the App's installer, and run it.  Repair Sims 4: open your game library, click Sims 4, and select Manage > Repair.  Try again to play, with nothing else running on your computer, and let me know what happens.