Several fixes can be used to solve the "SD card not showing up on Steam Deck" issue.
Way 1: Restart your Steam Deck
Your Steam Deck may have problems recognizing your SD card if some random bug or glitch occurs. Usually, rebooting your device is the best way to remove them.
Way 2: Remove and reinsert the SD card
If the problem wasn't solved after a reboot, you can shut down Steam Deck and remove the SD card. Then power it up and reinsert the SD card.
Way 3: Check the charge
Your device may show this kind of error when it has a charge of less than 20%. To avoid it, you need to ensure the Steam Deck has a charge of at least 20% before connecting the SD card to it.
Way 4: Try a different device
It's possible that your SD card is failing or has been damaged. You can use it with a different device like a Linux PC to see if it works consistently. If not, you may need to purchase a new SD card.
Way 5: Format the SD card
When nothing works, you can always reformat the SD card to fix the file system-related issues. Note that reformatting will erase all data on the SD card, so you'll need to redownload the games afterward. Although you might not find the SD card in the Storage section, you likely still are able to format it using the steps below:
- Click the Steam button beneath the left touchpad.
- Select Settings.
- Scroll down and click "Format SD card."
- Click "Format" again.