CD/DVD drive missing can be caused by various reasons like Windows 10 update, corrupt driver, out of date firmware, or a factory defect. You say you just upgrade to Windows 10, it might be the culprit. You can try the tips below to see whether it's working:
1. reinstall or update device driver
2. uninstall IDE ATA/ATAPI controllers in Device Manager
3. make changes to the Windows 10 registry.