It's a long-standing bug in Kodi affecting multiple Linux distro's. If you reboot with the disk inserted the Play menu should be visible.
Hi, I too am experiencing this issue since upgrading to the new "Estuary" skin; the "Disc" menu item does not appear under any circumstances, for either audio CDs or DVDs.
Some audio CDs will autoplay, or rip, but multi-session CDs with "Extra" content just mount the disc as removable media, DVDs are mounted in the same way.
Rebooting with a disc in the drive makes no difference.
OpenElec and version 7.0.2 of LibreElec using the confluence skin used to present a "Disc" menu item on this same hardware.
System info and logs using the new submit log function, for your viewing pleasure:
RBEP
Regards and thanks