Every hard drive be it portable or fixed in a system.
Is constantly spinning the platter, the magnetic platter the data is stored on.
The read write heads during a read write are moving across the platter.
There are two cases where you can damage the information of the platter making the drive none responsive.
The device may be detected when plugged in but access to the drive and files or its contents is not displayed.
This is because all hard drives need to shut down correctly or corruption of data or parking of the read write heads of the drive are not performed.
Parking of the heads is a zone where the read write heads lock to the inner outer edge of the disk platter to avoid damage to parts of the platter that contain data.
This is very important if the drive is of a portable type since it is moved around and can be knocked.
The drive if not moved or knocked, needs to be checked for disk errors and repaired. or if the drive spins and makes a buzzing sound it means the heads may be stuck or locked . due to an improper shut down.
When you pause a copy operation the head just hovers above the data it reads or copies next, waiting for a resume. so if you disconnect the drive.
It has no chance of parking the heads back to the safe zone.
You need to scan the disk and fix the errors. If you can see a drive letter but cannot access the drive or see the data or files contained on it.
If the read write heads are not physically stuck it should fix the problem.
Make sure an operation is performed and never shut the drive down if you have paused an operation. cancel it if paused. or you will likely produce a corruption of the data of the drive. When a sudden disconnect is performed. be it by a driver or removing the power from the device.
As I said if you can see the physical drive letter of the device but have no access to opening it then the drive structure is corrupted and needs to be fixed by a scan disk via windows. or check for errors.
If file structure or mapping of data on the drive is corrupt it has no means of locating the data and its position of it on the drive. So the information or markers of where the data is or can be found need to be fixed. The file structure.