If you need help with the library GxEPD2, you should look at ZinggJM/GxEPD2 · Discussions · GitHub.
Compare the inking on the flexible connector with the inking of the author's panels found in
GxEPD2_display_selection_new_style.h
Report the inking you see.
Report the board you select to compile for.
You can find the default HW SPI pins used then e.g. in
arduino-esp32/variants/esp32s3/pins_arduino.h at master · espressif/arduino-esp32 · GitHub
static const uint8_t SS = 10;
static const uint8_t MOSI = 11;
static const uint8_t MISO = 13;
static const uint8_t SCK = 12;
If you need to use different pins, then you need to re-map the HW SPI pins.
See in [GxEPD2_Example.ino] (GxEPD2/examples/GxEPD2_Example/GxEPD2_Example.ino at master · ZinggJM/GxEPD2 · GitHub) how you can do this.
Make sure that pin 1 of your display panel is connected to pin 1 of your adapter board.
If the frontside of the panel faces up, then the component side of the adapter board should also face up.
Good Luck!