My Seagate 4TB HDD doesn't mount in OSX El Capitan on my MacBook Retina. I have been using it for the last week on this computer, but today it doesn't mount. It shows up in Disk Utility, but when I click "mount" it doesn't.
I ran First Aid on it and it still doesn't mount.
I tried it on an iMac with the same results, but other drives work fine.
I tried to shut down, restart - same outcome
on a different computer iMac - same outcome
different drive solid state and normal - both worked fine I ran First Aid in Disk Utility