@SLFGunnett Go into Documents > Electronic Arts > The Sims 4, open Options.ini, search for fullscreen , and set it to 0 (zero). This is where the game stores your graphics options (and much more). The edit will force windowed mode, at least until you change the setting again.
You can try going back to fullscreen mode after your game loads, but at the same time, change the resolution to match your monitor.
If this doesn't help, please run a dxdiag and attach it to your reply.
https://help.ea.com/en/help/pc/how-to-gather-dxdiag-information/
Hey, did set Fullscreen to zero but that didn't fix the issue, probably just some weird timing, here are this dxdiag's I ran.
@SLFGunnett Please update your system drivers using the Dell support site. I believe this is your model:
https://www.dell.com/support/product-details/en-ie/product/precision-3460-workstation/drivers
But you can click Identify Device to confirm. Update the BIOS first, and restart, then install whatever else Dell says you need. The AMD graphics driver at least has a newer version. Restart again afterwards, then try to play.
It's a good idea to disable Game Mode and Game Bar as well, both under Windows Settings > Gaming.
As a side note, you'd get better performance in Sims 4 if you connected your monitor to the graphics card, instead of the motherboard as you've currently done. I think you'd need a DisplayPort Mini to DisplayPort (regular) adapter, as in, the GPU only has DP Mini ports. Decent adapters are cheap and sold in any electronics storefront.
