Dimmed Screen

@ZoomerGirl  Do you play with the laptop plugged in, and if not, does it help?  Does it make a difference if you switch from fullscreen to windowed mode or vice versa?

Please also run a dxdiag and attach it to a post.

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

I always plug it in when I play my sims (I play for hours on end) 
I did bring the game up without the plug, it stayed bright, minimized and went back (IK some people have a problem of it going dim) and it did still stay dark.
Windowed screen usually stays bright but my laptop keeps changing back to fullscreen when i do it plus its a lil annoying anyway.
I don't know what settings make the screen go darker with the plug in (I thought I did all of those already)

Sorry minimized and came back and it still stayed bright (IDK why I wrote dark)

@ZoomerGirl  Your dxdiag shows a number of Windows errors that are worth addressing first.  So please run a couple of basic checks of your Windows system files:

• 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.

For Sims 4 itself, try disabling Game Mode and Game Bar, both found under Windows settings > Gaming.  (And then restart yoru computer.)  If that doesn't help, let me know whether using "windowed fullscreen" makes a difference.

If the game keeps reverting to fullscreen mode, try moving options.ini out of Documents > Electronic Arts > The Sims 4 and onto your desktop.  This file stores all your game options, so you'll need to redo other settings as well, but if the reason your settings rever is that this file is corrupt, forcing the game to spawn a new one is the only fix.

No error code

Windows Resource Protection did not find any integrity violations.
Going to restart now.

Up to date on computer updates.
Game mode and bar have been off.
Windowed Fullscreen goes dimmer. 

@ZoomerGirl  Try setting Windows to run Sims 4 in high-performance mode.  Hit Windows key-i and select System > Display > Graphics settings, click Browse, choose TS4_x64.exe, select the high-performance option, and save.

If that doesn't help, try changing the overall power mode.  Click the battery icon in the lower-right corner and drag the slider all the way to the right.  If this doesn't make a difference, you can revert the setting.

And of course please keep testing with the laptop plugged in.

Still goes dimmer.
Only things ATM that make it stay bright is windowed mode (So annoying tho) and keeping the laptop unplugged.
Anything fullscreen makes it dimmer for some reason.

@ZoomerGirl  There's one more place to check a few settings.  Hit Windows key-R and enter "control" without quotes, then click Hardware and Sound > Power Options.  Switch to High performance (it might be hidden until you click Show additional plans) and see whether this helps by itself.  If not, go back to this screen and click "Change plan settings" for the high performance option.  Then for both battery and plugged in, change the value for "turn off the display" to 30 minutes and "put the computer to sleep" to 45.  Turn up the brightness for both as well, either to the max or to something close that looks good to you, and make sure they match.  Then restart your computer.

These aren't optimal settings for a laptop; the point is to see whether they make a difference.  If they do, we can experiment with the settings to figure out the best balance between screen brightness and battery life.  Please also let me know if this merely pushes back the time when your screen dims to 30 minutes, or whatever the default setting is before you change the "turn off the display" value.

Finally, if the doesn't help either, go back to the "Change plan settings" screen, click "Change advanced power settings," open Display, and set "dimmed display brightness" to 100% for plugged in.  (You can set it lower if you prefer; the point is to raise it from its current setting.)  If this doesn't make a difference either, please open every category under Display and post a screenshot so I can see all your options.  These can vary greatly from one system to another, so I have no way of knowing what other settings your laptop might offer.

I dont have a couple of options that you said.

If i create and change power plan to high performance it dims my screen, I dont have a option to turn up the brightness on that either