The operation couldn’t be completed. (com.apple.DiskManagement error -69874.)

I just installed Paragon NTFS for Mac, on a laptop with MacOS Sierra. I downloaded the free version of 14, and even though I used to mount a Seagate 4TB drive successfully before, now I can't mount this drive after installing 14. It is activated, and when I try to run Disk Utility it says the partition is damaged, and gives the error "The operation couldn’t be completed. (com.apple.DiskManagement error -69874.)" I haven't had a chance to back up this drive yet, so I don't want to erase it, it has over 2 terabytes of data. I was going to use a new disk to back it up to, but now that one won't mount either, giving the same error when I try to use Disk Utility on it.

Do I have to use version 15, or are the disks ruined for good?