Hi

. . . . recently I used a DVD-R disk . . . .the disk back it wasn't recognised, . . .

Have you tried playing the DVD in the computer?

The following are possible causes of the problem:-

1. The disc is incompatible with the DVD player.
    
2. The disc is faulty, even though it burned to completion in the computer

I always burn to quality DVD-R or BD-RE for the initial burns and test in DVD and / or BD player, if the movie is OK then I use Nero to copy to DVD-R or BD-R discs.

The only time I have had a problem with DVD-R discs is when I tried a cheap one which used a different dye which was quite pale compared to the ones I normally use.

HTH

John EB