Seagate 5TB macos format error

Here's what I would try. First run
```
diskutil list
```
to get the name to the disk you're trying to format. The below commands assume this is "disk1", but replace "disk1" with the correct disk if it's something different.

Now unmount the disk:
```
diskutil unmountDisk force disk1
```
and then write zeros to the boot sector:
```
sudo dd if=/dev/zero of=/dev/disk1 bs=1024 count=1024
```
finally attempt to partition it again:
```
diskutil partitionDisk disk1 GPT JHFS+ "My External HD" 0g
```