I have a Creality Ender 3 Pro and recently fitted the BTT miniboard and TFT display.
When I tried to make the first print the machine would no longer read from the uSD card socket. When I contacted support they replied:
Please send the M21 command, if it shows SD init fail. It indicates that the onboard SD card function in the firmware of the motherboard is not turned on.
Need to be modified in the firmware. Please modify according to the following picture.