Drive Detected but Not Working?

1. Read the error instead of retrying

“The operation can’t be completed” on a copy, folders that spin forever, or files that open as garbage — that’s Disk Utility’s job, not another Finder refresh. If you already saw I/O errors, stop writing. Every extra save makes recovery worse.

2. First Aid on the volume you actually use

Select that volume in Disk Utility and run First Aid. If the disk uses APFS you may have a container above it — still start with the volume you mount in Finder, then walk upward if you need to, same idea as the Won’t Mount page.

3. Check whether the Mac can even write this format

Select the disk in Finder, File > Get Info, and look at Format. APFS, Mac OS Extended (Journaled), and exFAT are the ones I expect to write from a modern Mac. MS-DOS (FAT) works for small sticks with annoying name limits.

NTFS is the Windows default. A Mac will usually mount it and refuse to write without extra software. That looks like a broken disk. It isn’t. It’s a format mismatch.

4. Permissions and locked files

Get Info also has a Sharing & Permissions block. A disk copied from another user account can look “broken” when you just aren’t allowed to write. That’s fixable without Erase if the format is otherwise fine.

Locked files and a full disk are the other two mundane causes. Check free space before you run First Aid for an hour.

5. When the disk is simply failing

Slow folder opens, names that turn into nonsense, repeating I/O alerts, a copy that dies at a random file each time — copy off what you can and replace the drive. Formatting a dying disk gives you a blank dying disk.