Sounds like a corrupted or wrong firmware . First you have do determine if your Ender came with the new 4.x.x boards( you have to take the cover off and you will see it printed on the board) which are now 32bit with a bootloader pre-installed . If it does , then you can use the SD card to flash the firmware. It may fail few times but eventually it will flash. Re-formatting, trying different SD cards and different storage sizes are few things you can try. However, if you have an original Ender with 1.x.x boards then the flashing process is bit more complicated because these boards are only 8 bit with no bootloader installed. If you search for Teaching tech, Thomas Sanladerer , or CHEP on YouTube. They have plenty of detail and step by step videos for the Ender 3 and the flashing process. Good luck.