I was able to copy files from a friend’s MacBook to my external drive no problem but it won’t work with my MacBook. I understand I’d have to reformat but i don’t want to do that. How did it work with my friend’s MacBook but not mine?
Check the file system type. If it’s NTFS, your friend must have had NTFS drivers installed. Macs can read but not write to NTFS unless you install Paragon drivers.