After plugging the pendrive in the device, go to device manager (In run type "devmgmt.msc") In Device manager go to "Universal serial bus controllers". It should list the storage devices that you have connected to your PC. Right click and then click "Uninstall. Remove the pendrive and restart your system.
Try connecting the device again, I think this should solve the problem.
1) Some time pen drive showing in device manger but not in my computer , in other system its showing , so might be possible no drive letter assign for drive
> go to control panel > Computer management > disk management > select storage or drive which is not showing > assign letter select any latter
after doing above pen drive showing in my computer