RE: DVD-RW Drive Not Working - Dell Inspiron 15R 5521
Osprey, one of our more knowledgeable community members, posted some FAQ documents about troubleshooting DVD/CD drive issues. Check those out, especially the Osprey Optical drive Troubleshooting Guide, there are a lot of good steps that you can try that may resolve the problem for you.
I'm not sure what is happening with your drive but hopefully that information that Osprey posted will help. Let us know what helps resolve the problem, and if nothing does, we'll see what else we can suggest that may.