I recorded a tv show on a DVD recorder at my hi-fi system. It is beautiful there. It plays well there.
I took the CD to my computer. It shows up as a read only folder called Sonata_volume, and there is nothing in the folder. Getting info on it shows that it is formatted UDF, with 4.3 GB used.

sony rdr-vx500 is the recorder. I finalized the disc. It plays just fine in my sony recorders and players. But not on the Mac.

I tried to see it with toast, but that did not work either. It just shows up as a locked folder named SONATA_VOLUME

VLC sees the same SONATA_VOLUME, but again there is nothing in it, and it does not play.

Is there any way Toast can copy this DVD into a format my Mac can read?

With most discs recorded on standalone recorders Toast can copy the disc using the Copy window and it can extract the videos from the disc using the Media Browser. However, a few users are reporting that the titles appear locked in the Media Browser and cannot be extracted by Toast. Yours is the first I've heard that doesn't even display a VIDEO_TS folder in the Finder and doesn't play on the Mac.

I don't know what to suggest other than trying again with a different brand or type of media. Try DVD-R, DVD+R, DVD-RW or DVD+RW. Also, Toast can extract VR-mode titles from an unfinalized VR-mode disc.