unrecognized graphics card

Are other games affected? By system file checker do you mean verifying game files?

My top 2 guesses are a weird driver, or perhaps the GPU isn't quite seated nicely in the motherboard slot. 

Drivers should be relatively easy to reinstall. If it's Nvidia they even have a bit in the "custom installation" to do a clean install and make sure its all fresh. Can't recall how it all works with AMD cards as I don't use em, but should be a similar job. As for reseating just honestly give it a nice nudge, ensure power cables are fully clicked, etc etc.

Imjustbetter2445​  The fact that your GPU is unrecognized is not in itself a problem.  It's worht confirming that the game is properly using the graphics card though.  Open Config.log, inside Documents > Electronic Arts > The Sims 4, scroll down to Graphics Device Info, about 30 lines down, and make sure your GPU is listed there.  If you see anything else, please post that section of the file; stop when you get to Options.

If your GPU is listed but you're still seeing performance issues, please provide a dxdiag.  Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop.  From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.