My cd drive will not recognize a blank cd or dvd what can I do

It's difficult to produce a useful reply with so little information.

Computer operating system including version and/or service pack information?

Does the drive show in your file management application?

Does dive recognize commercially produced media like movies and music CDs? Note that CDs and DVDs use separate lasers within the drive. Failure of one of those lasers might allow the drive to use one type of media while completely ignoring the other.

Using rewritable disks (RW designation) or write once media? If write once media, is it designated "-R" or "+R"? Does the system or drive documentation indicate compatibility with both types or only one of the two?

Was the drive included with the computer? If it wasn't, did any software installation media come with it?

Install, uninstall or update any software recently? Any recent operating system updates? Have you scanned for malicious software like viruses?