My late 2011 13" MBP running Sierra won't recognize my Seagate external HDD in finder. It shows up in Disk Utility and I plugged it into one of our windows computers here at work and it showed up. I have only ever used this drive with my MacBook and it worked perfectly when I first got it but I was running El Capitan back then. I tried using the first aid feature in Disk Utility and it did nothing. I tried to mount the drive and it did nothing as well. I am not sure what to do next.