Q: OS Sierra doesn’t recognize external harddrive

Hi all,

I updated to OS Sierra yesterday, and and external harddrive (Seagate BUP Slim BK Media) that has been working fine under El Capitan doesn’t show up anymore. It’s connected via USB, and the harddrive utility finds it, but it is greyed out. Underneath the volume’s name, it says it is not initialized, and it has a Windows NT filesystem. I tried hitting the activate-button, but nothing happens. 

What can I do, short of erasing and reformatting the whole thing?

Thanks,
Ben