apple external superdrive not noticing blank dvd-r's

I have a external apple superdrive and one day I needed to write a dvd. so I got the superdrive and put in my dvd-r, it did noting. it was not on my desktop or finder so I put in a old dvd-r that i wrote and it worked. I opened disc utility and I saw this. I tried reseting my smc but I still cant read/write Blank dvd-r's. one's I already made work