www.makemkv.com

MakeMKV was throwing a ton of read errors so I created an ISO using ddrescue which seemed perfectly happy. So I have the ISO, I can pull all of the files off to a folder. I did the "Backup" option and it created discattd.dat. Some other forum posts said simply put discattd.dat in the same directory all of the other files from the ISO are. This didn't work and I got "The volume key is unknown for this disc - video can't be decrypted". So I copied the entire MAKEMKV folder into the extracted files so I have

/AACS
/BDMV
/CERTIFICATE
/MAKEMKV

and I tried to open BDVM and that didn't work either with the same can't be decrypted error.

What am I doing wrong?

When you do the backup option in MakeMKV, you need to start an encrypted backup (uncheck "Decrypt video files") in order to create a discatt.dat (not discattd.dat). There will not be a MAKEMKV folder.

That was it. Thank you!