Pacific Digital quit burning

I have a Pacific Digital external DVD± burner that quit burning. At first I thought that it was a new batch of disks so I purchased another brand and they won’t work either. When I check a blank disk with Nero CD-DVD Speed, it says that the disk is closed. I am wondering if it is being closed during the lead-out because I was able to add data to another DVD that already had data on it.

I am able to read data and play DVD movies with the drive.

Any suggestions?