FIX an Error "a device which does not exist was specified"

Usually, when your external hard drive shows the "Drive is not accessible. Access is denied" error message, it is because you don't have the privilege of accessing your disk. Right-click on the inaccessible hard drive, select Properties.

You can try the below mentioned effective solution to make the drive partition accessible again:

 Method 1. Gain administrator permission 

Step 1: Open This PC, right-click the inaccessible hard drive, and select "Properties".
Step 2: Go to Security, click "Advanced" and "Owner".
Step 3: Click "Edit" and click your username under Group or username.
Step 4: Check all boxes under Allow column, click "OK" to confirm, and "Apply" to keep all changes.
Reboot PC.

 Method 2. Update the hard drive driver 

Step 1: Right-click on This PC/My Computer icon, select Manage and go to Device Manager.
Step 2: Expand Disk drivers, find and right-click on the hard drive, choose "Update driver".
Step 3: Select "Search automatically for updated driver software" and wait patiently till the process completes.
Reboot the PC.

 Method 3. Check and fix file system errors 

Step 1: Press Windows + R keys simultaneously to invoke Run. Type cmd in the empty box and hit Enter.
Step 2: Type disk part and click OK to bring it up.
Step 3: Type chkdsk G: /f /r /x and hit Enter.

Exit the command prompt and reboot your PC.

 Method 4. Format hard drive 

Format hard drive and change the file system to NTFS. Hope it will help you out.