Sandisk Ultra 16GB USB no longer working

Suddently I cannot use my USB - Windows Explorer no longer shows the drive and when I go into disk Management it shows the disk, but without a drive letter - try and do this, and I get ‘The System Cannot find the file specified’. I cannot reformat it - similar errors - any ideas?

If a port is used for multiple removable devices Windows sometimes assigns the same drive letter to each device which can cause some drives to not work.

When you see your 16GB USB drive in Disk Management assign a different drive letter to the drive. Something down the alphabet chain like U or S or X.

Once Windows can see the drive, open a Command Prompt and run a CHKDSK /F command for the new drive letter.

No, that didn’t work. Whilst it will create a simple volume it won’t format or assign a drive letter