Thank you for the details of the issue you are experiencing with your external hard drive. I recommend these steps when you are unable to eject the disk:
If you can’t eject an external disk
- Choose Apple menu > Log Out, and then log in again. Try to eject the disk again.
- If you still can’t eject the disk, choose Apple menu > Shut Down. Disconnect the disk from your computer, and then start up your computer again.
Thank you for using Apple Support Communities.