First try rebooting your device, if sd card still doesn't show, pull it out and make sure it's going in the right way. It supposed to click into slot, otherwise you'd have to force it in, and it won't work.
If it still doesn't show signs of life - pull it out, check the card slot on device with a light - make sure there are no signs of damage. If applicable - check sd card with another device to make sure card itself works.
Refer to [[ASUS MeMo Pad FHD10 Troubleshooting|Troubleshooting Page]] for more solutions. Check out the disassemble guide to take the tablet apart and see if any damage not visible through the slot hole.