How have you tried writing to DVD-R?
What software do you use to write the DVD discs?
Most software that writes to DVD and CD, allows the selection of what you wish to write before you start.
As an example in Nero, before you select Data, or Music type etc.. you have to select the correct drive.
But what it's easy to miss is that one drive can appear more than once in the list, i.e. once for CD, and again lower down for DVD.
So you have to select the drive in it's DVD incarnation to write to DVD discs.