[CURRENT ISSUE] Sims 4 Unable to Start, Initialization Error

@lorelei5  I would suggest running a malware scan.  I'm not saying your computer definitely has a virus, only that it's a reasonable possibility when a new Windows account works at first and then doesn't.  And it's best to find out either way.  Please download Malwarebytes (the free trial is fine) from here:

https://www.malwarebytes.com/mwb-download

Open it, click Scan > Custom Scan > Configure Scan, check all the boxes both for all scan types and for all your drives, and let it do its job.  This could take anywhere from a few minutes to several hours, depending on the amount of data and whether the scan finds anything., so you may want to set it to run while you're doing something else.  Please attach its report so I can take a look.

Whatever Malwarebytes finds, please run a couple of basic checks of your Windows system files next.

• 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.