Disk Could Not Be Partitioned - First Aid not helping I am trying to install Windows by Bootcamp on my MacBook Air (2017) 128 GB. I am using the newest macOS, so High Sierra. Unfortunately I am getting "Disk Could Not Be Partitioned" error. I tried to use First Aid and "/sbin/fsck -fy" from Single User Mode and there aren't any errors. 

What can I do to fix my problem?
I had very similar problem. After contacting Apple Support and following their instructions, I've reinstalled macos (instructions here). This is not a wipeout reinstall, but do make a backup. 

After the reinstall partitioning worked like a charm.