EXTERNAL HARD DRIVE NOT WRITABLE

AndresRU Said:

"Aid a couple times to try and repair it. However, no matter what I do, nothing seems to work and at this point I don't know what else to do. I know the hard drive works, I can drag and drop files from it to my computer, but not vice versa. Does anyone know a way to work around this? I'm getting really frustrated"

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You Must Format this Accordingly:

Is there any concern for loss of data? What's your macOS Version? For Sierra or later use APFS for the format type. If pre-Sierra, using

Format Accordingly:

As for using an external drive, export files on it (so that nothing is lost), then erase the drive, and then format it the applicable drive format: File system formats available in Disk Utility on Mac - Apple Support

Boot into Recovery Mode to perform this (Intel or Silicon).

In depth: What to Do:

Use Time Machine - and not a third party app. You would....

1. Open: Disk Utility***
2. Erase: the drive
3. Format: with the applicable format

***To Open Disk Utility: Boot in to Recovery Mode > Go to: Applications > Utilities

If you can't Erase it...

Mount the Hard Drive in Disk Utility:

While booted into Recovery Mode [Hold Down: command + R keys upon boot], go to Disk Utility> tap the Hard Drive, then tap the Mount button. See if you can then perform the erase. Also, perform this upon installing it, if necessary. If it is already mounted, then unmount it and then remount it. See where you can go from there.

I wonder if the issue is that the filesystem is HFS, and not HFS+.

It looks like Apple may have started deprecating plain HFS (not HFS+) in macOS 10.12 (Sierra). That wouldn't necessarily mean that all support would have gone away instantly. They might have phased HFS out in stages.

Sierra no more support HFS standard forma… - Apple Community

This reddit thread suggests that macOS 10.15 (Catalina) is incapable of reading plain HFS volumes.

https://www.reddit.com/r/MacOS/comments/g72j87/why_did_catalina_drop_support_for_standard_hfs/

AndresRU wrote:

However, no matter what I do, nothing seems to work and at this point I don't know what else to do. I know the hard drive works, I can drag and drop files from it to my computer, but not vice versa. Does anyone know a way to work around this? I'm getting really frustrated

If the issue is that this is a plain HFS drive … and the attempts to Erase it haven't already destroyed the data:

1. Get another hard drive.
2. Format it using HFS+ (Mac OS X Extended (Journaled)).
3. Copy all the files from the HFS volume to the HFS+ one.
4. Back up the new HFS+ volume somewhere.
5. Goal: A new HFS+ volume and backup that contain your data and are readable and writable.

Then you can figure out if there's some way to erase the old drive for reuse.