DVD-R (Read only).
One time recordable - are you trying to record?
My initial thought/thinking was that you were trying open movie DVD's etc. and that was what was failing. (Not recognized.)
Are the DVD's new and completely blank? What capacity?
Are you trying to save/write data to those Philips DVD's? Or perhaps recover data from them?
Very much the same questions but more information is needed.
E.g., the source of the DVDs you bought - the DVD's could be the wrong media, perhaps faulty, or even counterfeit.