Recorder will not read DVD discs

some discs don't work in some recorders. I always use verbatim, ritek or tdk discs and have very few problems. if the recorder suddenly dislikes a batch of one brand, I'll use one of the others.

Try cleaning lens first.

Sometimes a blank DVD will not be the proper format. Upgrades have been done to DVD-R disks, and your recorder might not recognize the upgraded format on the newer disks. This has happened with Philips, Emerson machines- they all use a Funai burner. I have found with my FUNAI/Philips/Emerson recorder that purchasing the Philips, 1-16 speed DVD-R blank disks fixes this problem on my 2 machines. If you have an older DVD-RW 2 speed disk, it should work as well.

because there is nothing to read in blank cd rw , because dvd operating system is not meant to write cd ,but only to read the disk

Yep, replace unit since electronics have gone south on you.

Did the sales guy use the same DVD-RW that you did? Maybe the brand you are using is not of good quality and can not be recognized by the recorder. If he did not use the same disc did you notice if he used DVD-RW or DVD+RW? Some DVD-Recorders only recognize one or the other but this is kind of rare these days. I recommend verbatim brand discs. They should be available for sale at any shop. If you want the ultimate in quality DVDs then go with Taiyo Yuden. This Japanese brand invented recordable media and in addition to that they are obsessed with quality. www.supermediastore.com is always where I get my discs.

Thanks for reading!
Hope this was helpful

You need to use DVD software such as Nero that supports DVD-RW. from the app is where you would erase and so on
also make sure your blanks are +RW and not -RW

Some DVD recorders don't like certain types of media. Does this happen with all blank dvd+rw disks or just with that specific brand? If it's that brand then you should just use a different one.

I've found that once a disk is formatted in certain formats with a pc it prevents the LG from reading it.  Format it again in the LG (if you can!) or use the pc to format it using the UDF1.5 setting in a pc (which sort of resets it so the LG can at least see it as an unused disc again). 

All in all I have found my RH19991H really confusing as far as disk initialization and formatting and finalizing is concerned.  Sometimes you can select to finalize a +-rw dvd and sometimes not (the latter is the the case according to the manual) and sometimes I can select the format mode and sometimes not.  Sometimes the machine auto finalizes the dvd+-rw (the way it should be says the manual) and sometimes it does not and then I cannot use it in the pc.  I have also created some disks with DivX files and was able to play them in the LG and then using the same pc, same type of discs, same video editing software and same settings created other DivX files I could not play on the LG.  It seems the software on the machine needs some work...

your dvd writer is bad you will have to replace it believe me i now what im talking about i have went through 4 ilo's did the same thing plus 100's of differnt name brand dvd's