First, make sure that the SD card is inserted properly. Also, check with a good light and magnification for any debris in the SD card slot. Vertical SD card slots are prone to collecting fine wisps of filament and other unwanted material which may interfere with proper operation.
If you continue to have difficulty, then try a different SD card. It may be that your current SD simply does not work with your printer. Many printers, including genuine MakerBot printers, have borderline SD card electronics which do not perform well. An SD card which works fine with your computer may not work well with your printer, hence the recommendation to try a different card.
Also, make sure that the SD card is formatted as either FAT-16 or FAT-32 or FAT-32. The proprietary “eFAT” format is not supported as it requires licensing from Microsoft.
Check that the files in question end with either the .s3g or .x3g extensions. Sailfish recognizes files in lower, upper, and mixed case. Files which do not end in either of those extensions will not be displayed, unless they are the names of folders. Also, if the files you are looking for are in a folder, then you will need to navigate to that folder in order to access them. See Section 3.3 for further details on working with SD card folders.
Note also that filenames longer than 31 characters, filenames with spaces, and filenames with non-US-ASCII characters may be problematic. There are special “extensions” to the FAT-16 and FAT-32 file systems for those categories of file names. Your printer’s tiny microprocessor does not have space for the additional code to handle these extensions.
If your prints from an SD card failed with the printer simply stopping midprint without displaying an error message or clearing the platform, then there are several likely causes, described below:
Another cause of truncated files is a known bug in many firmwares. The SD card library used by many firmwares has a bug which can truncate SD card files. The file will print fine at least once and then be truncated and print incorrectly afterwords. This bug has been fixed in Sailfish 7.6 and the author of the SD card library notified. The bug has not been fixed in “stock” firmwares.