Problem with DVD-R/RW

I have got Liteon SHW-1635S DVDRW.
Initially when I got it everything was all well but then it stopped recognizing any media.
I got it repaired by the service center, probably they gave me a refurbished one.
Now it does not read any R or RW media that has been burnt on a different machine (at various speeds). It does recognize pressed DVD’s. Have tried to re flash to latest ROM version.

Any suggestions?? or is it back to the service center???

Try with pressed DVD media. If it can read those, most likely the issues come from the burned media (other burner).