Monoprice printer: no files found on SD card
I've no idea why 3D printers don't like SD cards formatted by operating system utilities, but they don't. Use SD Memory Card Formatter to format your memory cards. Unfortunately, you have probably lost any data that was on the original SD card.

The SD cards that are supplied with 3D printers typically contain documentation, test files, and device drivers. However, these files do not need to be present for the correct operation of the printer. All that is needed is a correctly-formatted SD card containing the G-code files that you want to print.