why won't my dmr - e75v panasonic dvd recorder read it's own discs?

It will not play or read any dvd r's. It was purchased before 2005 and I am aware that they say it won't read DVD - or + r discs. The fact is these are discs that did load into the recorder. I recorded many things on many discs. Why has the machine all of the sudden stopped reading the discs. There are some discs I never finalized and now it won't read them to finish the discs.