Seagate Backup Plus Ultra Touch, Locked.

Did you use the Seagate proprietary software to enable the drive's hardware encryption feature? If so, then you will need to use that same software to unlock the drive or to disable the hardware encryption.

FYI, macOS can read from an NTFS volume without any third party software. You only need the third party NTFS driver if you wish to write to an NTFS volume with macOS. Most contributors here would recommend changing the file system to one macOS has full native support.....HFS+ or APFS, or if you need to share with a Windows computer, then exFAT.

There are a lot of different ways a drive can be locked. Can you show a screenshot of the message? Or how you determined the drive is locked?

Edit: Can you see the actual volumes/partitions on the "locked" drive? Can you mount it? Or read it? Or is the problem only with writing to the drive?