I was trying to follow a tutorial online that included using diskpart on Windows 10 to format my 1TB external drive, with commands such as clean and partition. But after learning that it would not produce the results I wanted, I decided to stop and erase the disk from Disk Utility on macOS Sierra (10.12.4). So I completely erased it and formatted it as Mac OS Extended Journaled, but now I am unable to partition the drive because the button is greyed out.
I have tried erasing the drive multiple times, including writing zeros over the data (which took forever) but nothing has changed. Help?
Mac mini (Late 2014)
2.6 GHz Intel Core i5
macOS Sierra 10.12.4