File manager doesnt see the external sd

[AC Question]

Polaroid 902b tablet It went haywire withe flickering screen so I shut it down and rebooted then most of the apps wouldn't work so I reinstalled them. Now the file manager(I've tried 3of them) won't recognize the external SD card or my USB when I plug it in.
What could be wrong?

 

[B. Diddy]

Welcome to Android Central! Go to Settings>Storage​--does the system even recognize the SD card as being inserted? If not, remove the card and insert it into your computer. Does your computer recognize it?