As far as I'm aware, StoneAge Gamer just takes krikzz's flash carts, and puts their own branding on them, with some extra packaging options. All of krikzz's flash carts require an "OS" firmware in order to function. If it's an older flash cart, I'm going to assume it's not an FXPAK PRO. Do you know whether it's a Super Everdrive or an SD2SNES? The latter seems to have been completely deprecated, so I'm not sure where the firmware for that would be located now.
If it's a Super Everdrive X-series, then the OS files are here:
http://krikzz.com/pub/support/super-everdrive/x-series/OS/If it's an older Super Everdrive, then these would be the OS files for it:
http://krikzz.com/pub/support/super-everdrive/v2/OS/I probably wouldn't just install them, and pray. You'll probably want to actually figure out which type of SNES flash cart it is, first. Also, I would just go ahead and make sure that the SD card is formatted as FAT32. You could also look on the SD card to see if there's already firmware installed on it. If there is, there should be a folder on the route that's probably labeled "SPED," or maybe "SD2SNES," with an "OS.SMC" file inside.
EDIT: Here's the
SD2SNES project firmware page, with instructions for installing, if that happens to be what you have.