Why has my phone stopped recognizing its memory card?

Start by treating the card as potentially valuable, not as something to reset. A recognition problem can have several explanations: the card may be seated incorrectly, have visible damage or debris, use a file format the phone does not support, or be faulty. These are possibilities to investigate, not a diagnosis.

Use the instructions for your particular phone model before opening its tray. For Samsung Galaxy devices, Samsung advises turning the device off before ejecting the tray, then checking for visible damage and wiping dust or debris with a soft cloth. Tray steps can differ between models, so do not assume another phone uses the same procedure. [S1]

First, check the phone maker’s model-specific instructions for removing the card. If those instructions call for switching the phone off, do that before ejecting the tray. Handle the card carefully and look for obvious cracks, bends, or dirt; do not scrape or force it. Samsung recommends checking for visible damage and using a soft cloth to wipe dust or debris from the card. [S1]

Then reinsert it according to the phone’s instructions, making sure it sits as directed rather than forcing the tray. Samsung’s troubleshooting guidance also recommends removing and correctly reinserting a microSD card, but its steps are for Samsung devices and are not universal. [S2] If anything looks damaged or the tray does not move as expected, stop and consult the phone maker or a qualified repair provider.

You can try the card in another compatible device to help narrow down whether the issue is limited to the phone. Samsung recommends testing the card in another device. Its guidance notes that a PC may support file systems that Android does not, so a card working on a PC does not by itself prove that its format is supported by your phone. [S2]

If another device offers to format the card, cancel that prompt if you need the files. Avoid choosing format or repair options during this check. Samsung warns that formatting erases data and recommends backing up important data first. [S2] The guidance here does not establish how to recover files from a card that is damaged, unreadable, or not backed up.

Record what happened and which checks you performed, without claiming more than you observed. For example:

“Phone: [make and model]. Card: [type/capacity, if known]. First noticed: [date or approximate time]. Phone message: [exact wording, or ‘none’]. Visible damage or debris: [what I saw]. Reseated using: [model-specific instructions]. Tested in: [device type]. Result: [recognized / not recognized / asked to format]. Important files backed up: [yes / no / unsure]. No format performed: [yes / no].”

If the card contains important files that are not backed up, keep avoiding format prompts and tell a qualified support provider that preserving the data matters. If you have a backup, replacement may be an option, but these checks alone cannot confirm that a card is defective or identify the right replacement for every phone. Use your phone maker’s compatibility guidance before buying one.