First off, I have never heard of "Samysong". Second, the first thing to check is the software you are using with the drive. Beyond that, it starts to get complicated. We need more information. COMPLETE specifications of your PC (Make, Model, or components if home built) and what software you are using to play the DVD.
If the drive is otherwise functional, you probably don't have a DVD decoder installed. They are not free. You might also try a different player software like VLC Player. If it turns out to be a drive problem just replace the drive. DVD burners are under $20.
Appreciate the response to inquires about the CDDVDW TS-L633C. My bad, referencing Samysong. The CDDVDW TS-L633C has burned well, but I have had continuous problems reading. I see that I am not the only one with this problem concerning this model CDDVDW TS-L633C. The frustration, time and again, are not worth it. As per suggestion, I have purchased a different external model. Again, thank you for the responses.