I don't have a fix for this, just a similar but not identical issue. I have been happily printing with my Ender-5 for about 7 months now. I have not recently flashed or upgraded nor changed my SD card. I was in the middle of a print when the print suddenly froze. THe ender 5 indicated that no sd card was inserted. I made sure that it was clicked into the proper position. Thinking that the microsd had somehow become corrupt in mid print, I for matted another and inserted it, but again the printer refused to recognize that a card was inserted. Because this issue suddenly appeared mid print I am wondering if this issue is a hardware problem with the reader in the printer.