You need to provide more information in order that someone may address the problem, rather than guessing what the problem might be.
If you want guesses, here are just a few:
If you have an unfinalized DVD from another DVD recorder brand you should finalize it on that brand.
If you have recorded a DVD in a VR format on another brand of DVD recorder, see that recorder’s manual for the procedure to “make recording compatible.”
If you have a DVD edited or created on a computer it may not be in a format compatible with your Panasonic.
You may be using inferior no-name or Memorex media.
If your Panasonic reports “no read” you may have a dirty or failed lens or the DVD drive rubber hub may have a build-up of dust, debris or oily residue resulting in read, write or finalizing errors; all conditions that indicate that it’s time to service the DVD drive. There may be other problems with your Panasonic.