Why can’t I duplicate my laptop screen anymore?

I've been using my laptop with two external monitors for about two years now, usually duplicating the laptop screen to the first external monitor while extending to the third. Recently, without any new updates or changes, I found that I can no longer duplicate the laptop screen. When I try to use the Windows settings to duplicate, it only works for a second or two before the second monitor reverts to extended mode, even after I click to save the settings. All screens are detected correctly and have the same resolution, so I'm puzzled about what's going wrong. I can duplicate the two external monitors without issues, but the laptop screen just won't cooperate. I heard some people mention using the NVIDIA tool, but it only displays the two external monitors. Any advice on how to fix this issue?