not recognising them as recordable discs. ?

I have a DVD Recorder DMR-EZ45VEBS (2 years old). Although I am inserting the same recordable discs that I have been using for some time the recorder is All the discs have been formatted, some are blank, some have recordings on them that I have finalised and some recordings are unfinalised. When I go into the 'functions' button the 'management' option in the menu doesn’t appear and I am unable to reformat the discs. When I go into the 'direct navigator' it doesn’t not open.

Purchased discs play Okay. It would seem to me that the reader is no longer working, is this the case? and if so what, if anything can be done by me or do I need to consult an engineer?

In ether case if it is the reader can it be rectified?