If the board is a new board, the OLED should display by default. The OLED was operated by SPI3 of STM32L462, and the display reset is controlled by PH1 of STM32L462.
it is better to start or recover to default configuration.
user may get some binary or source files from x-cube-cellular website https://www.st.com/en/embedded-software/x-cube-cellular.html, then you can find the binary at (or similar location) STM32CubeExpansion_CELLULAR_V5.2.0\Projects\B_L462E\Demonstrations\Cellular\Binaries\l462_t1se_socket_v520.bin