dvd problems
My iMac has stopped recognising the external DVD device which will accept a DVD/CD, apparently rad it and then elect it. The DVD is not included in the systems information.
Try restarting in Safe Mode per the directions in
Use safe mode to isolate issues with your Mac
If you still have issues, then try:
How to reset NVRAM on your Mac
If you continue to have DVD problems then change the USB cable and or the DVD drive.