MKS_SGEN_L_V2 LCD problem??

Marlin 2.0.7.2 (f74015b 22 days ago)

I cannot use the SD card attached to the LCD with MKS_SGEN_L_V2
There is no beep.
LCD display normal
Rotary encoder normal
STOP switch normal
The MAINBOARD SD card is not recognized as a windows drive.

Is this the correct behavior?
Is there a mistake in the config?
or mainboard broken?

hardware check
It works fine when I connect the LCD to another mainboard.
test SKR1.4
SD,LCD,encoder,beep,stop swich,WindowsDRIVE ALL OK

TEST LCD (Of course, they are config one by one)
// [reprap.org]
//
#define MKS_MINI_12864

// [reprap.org]
//
#define REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER

In your boards pin.h file

#ifndef SDCARD_CONNECTION
#define SDCARD_CONNECTION ONBOARD
#endif

Ie it will use the onboard sd card unless you enable #define SDCARD_CONNECTION LCD In Configuration_adv.h

Now as for OS access to the sdcard, it is either marlin access or OS access not both at the same time.
you have to release the sd card from marlin to give it back to the OS (it is a option on the lcd setting and a gcode)

thanks Dust
host drive access is success