Hi Frank, welcome and thank you for your question. My name is ***** ***** I am glad to assist you today.
Are you using a Windows computer or a Mac? This normally happens when there is a program running in the background that holds a lock or access to the USB drive, causing Windows not to be able to eject the drive.
Have you checked if certain software, specially those that came with the drive, are still running?
Please let me know by replying to me here so that I can help you further.