Mac Mini DVD boot issue

Installed OpenSuse 42.2 on late 2009 Mac Mini. EFI boot works just fine. But I can’t boot from DVD anymore. Tried the Mac boot keys, does not work. Has anyone encountered this issue? And is there a solution? Thanks.

That’s pretty old hardware and DVD players are not known for their long life. Check it with another boot disk. Also check the disk on another system

As in powering the Mac up and holding the option key? Was the dvd working fine, I have a MacBook3,1 I just used the USB port to install the OS via option and select the USB device.