Try restarting the phone (just turn it completely off, wait a few minutes and then turn it back on). This may resolve the problem.
If it doesn't, then it could be an app on the phone, a virus or malware that is causing it not to recognize the SD card. You should check the device for that. You may also want to try starting up the device in "Safe Mode" and see if the card is recognized in that. If it is, then definitely check for things on the device that shouldn't be.
You should also check that there is nothing in the slot where the card goes. Dust, debris, crumbs, etc. and that nothing in there is bent. Then check the card itself for scratches, damage, etc.
Side Note: While cards are able to be taken in and out of a device, and put into others, they really are not made to withstand doing that all the time. Such use can easily damage a card.
In the end, if you can't read it, you may want to try connecting the device to a computer via USB cord and see if the computer can read the card through the phone, if not try connecting the card directly through the computer. If all of that fails, then the data on the card is lost.
To get into "Safe Mode" please do the following.
1. First turn off the phone.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.
Facebook
Twitter