Serial SPI Arduino 10.1"TFT LCD Display Shield RA8876

i bought the subject display from came with the 8876 shield. chip on the display itself is labeled ra8876l4n. i attached an ER-AS-RA8875 Arduino Shield and MEGA

I have used the vendor's library, but the compilation is wrong, I can't use it.
So I used the library at GitHub - xlatb/ra8876: Arduino library for interfacing with RA8876 graphics chip

I have used an extra 5V power supply but the screen only shows the backlight without showing any text
Can anyone tell me what went wrong?