As I explained in #23, #26, #29, the IDE comes with an "official" <SD.h> library.
The "official" <SD.h> library will work with the UNO digital #10, 11, 12, 13 on a UNO board.
There have been many "third party hacked SdFat.h" libraries that you can configure to bit-bash on a MEGA2560.
Even some of the older "official" SD.h libraries have special configurations to bit-bash with #10, 11, 12, 13 on a Mega.
Unfortunately, the current v1.6.12 IDE does not seem to have a configurable SD.h
I have no idea what hacked libraries you are using, how do you expect anyone to help?
David.