OTG storage devices stopped working
Try the app USB Device Info  it might assist with debugging USB issues.


  This application will provide information about almost all currently
  plugged-in USB device (see below for more info about the 'almost').
  
  Information includes: •The Device class •The USB device path •The
  Vendor ID (VID) and the Product ID (PID). •A List of all interfaces
  and their endpoints.
  
  If you download the accompanying databases, the application will also
  be able to provide you with additional info such as the Vendor of the
  device (which is not necessarily the brand!), the vendor's logo and
  the product name.
  
  This application uses two different methods to collect information:
  
  
  Android mode will use the native android USB API.
  Linux mode will parse /sys/bus/usb/devices/.