macOS 10.9.5 and higher won’t allow Sheepsaver to access optical drives unless the user who is running Sheepsaver is added as a member of the group operator which apparently is the group that deals optical disk volumes.

To check if your user is already a member of the group operator use this command:

dscacheutil -q group -a name operator

If your user is not already a member of the group operator, run this command to add them to the group:

sudo dscl . -append /Groups/operator GroupMembership $USER

And to remove your user from the group operator just run this command:

sudo dscl . -delete /Groups/operator GroupMembership $USER