Question: Can't copy or drag files to the external hard drive.
Earlier in Yosemite the files could have been copied or dragged into the hard drive. After upgrading to El Capitan, I can't do that anymore. Most of the people have suggested to re-format the hard drive, but that's not the solution. It will still not allow to copy or drag files into the hard drive.
MacBook Pro with Retina display, OS X El Capitan (10.11)