Try these troubleshooting tips:
1. Unplug mouse, then plug it back in or into a different port.
2. Try a different mouse.
3. Turn off "Display Pointer Trails" in the mouse control panel option.
Control Panel > Hardware and Sound > Select Mouse > Pointer Options. Under Visibility, un-check the Display pointer trails.
4. Try the tips in Crinrict's article - Mouse pointer is invisible
http://sims4.crinrict.com/en/2014/08/mouse-pointer-is-invisible/5. It has been reported that screen capture/recorders, instant messengers/video chat or VOIP programs, like Discord may cause issues with Sims 4 and may need to be turned off or uninstalled if issues are severe. Also turn off any overlay those programs may cause issues as well. This is to be sure the program and it's overlay isn't interfering with the game.
6. Turn off Focus Assist
Usually, if the mouse stops working on one portion of the screen it's because there's a notification underneath the game window waiting for a response. Try alt-tab to the desktop to see any notifications. You should be able to get rid of the problem by turning on focus assist.
Turn Focus assist on or off in Windows 10
https://support.microsoft.com/en-us/help/4026996/windows-10-turn-focus-assist-on-or-off7. Disable Game DVR and Game Bar. These are known to cause issues with some games.
How to Disable Windows 10’s Game DVR and Game Bar
https://www.howtogeek.com/273180/how-to-disable-windows-10s-game-dvr-and-game-bar/8. Deactivate Origin in Game:
Open Origin, Select Origin > Application Settings > Origin In Game and click the on/off switch to disable Origin In Game. - This will sometimes make the game not work correctly.
9. Repair Game:
In Origin > Games Library, right-click on Sims 4 and select Repair. - Do note this repairs the game's install files for the actual game. It does not make any changes to the saved game files. Meaning that your saved games are safe, they won't be deleted. If you'd like you can copy the Sims 4 folder to a USB key.
10. If you have mods or custom content installed, move the mods folder to the desktop. Clear game cache and delete the localthumbcache.package from inside the Sims 4 folder and try again. This helps troubleshoot game and mod/cc issues. - Load the game and see if the issues are still there.
-- Even if you don't play with mods or custom content installed, it's a good idea to clear game cache and the localthumbcache.package from the Sims 4 folder.
Delete Game Cache Files (What and How-To)
http://www.carls-sims-4-guide.com/forum/index.php?topic=29288.msg401662#msg401662How to Fix Problems with Mods/CC
http://www.carls-sims-4-guide.com/forum/index.php?topic=25031.msg426156#msg42615611. If the keyboard and mouse are lagging, try lowering the in-game graphics to see if that helps. It may be that your computer is having a hard time keeping up with what's going on in-game. Lowering the graphics may help with that.
12. Try running a clean boot, as this will help with stopping any other programs from interfering.
http://help.ea.com/en/article/how-to-clean-boot-your-pc/----
Reference Links:
Mouse cursor not working properly
https://answers.ea.com/t5/Technical-Issues-PC/Mouse-cursor-not-working-properly/td-p/3302073Keyboard not working In-Game (Tips)
http://www.carls-sims-4-guide.com/forum/index.php?topic=26724.msg445861#msg445861