My 3ds bottom screen is bright as normal then dim out (video included)

Hi,

When I turn it on, the bottom screen is bright as normal then it dims out immediately. When I open Settings or close Settings, the screen is also bright then dim.

Video: https://youtu.be/ud41qm7p4m8

It was updated to lastest version (11.14.0). I also did Format System Memory, set the brightness level to 5.

Please help fixing this error. Thank you!