Backup to CD not working

I can only guess … it worked on an old computer or Windows version (one which had all the drivers for writable CDs), but now, after an upgrade to a new Windows version or a new computer it no longer does …

Forget CDs. They're so “last millenium”. Change to using an external USB hard drive or USB memory stick. More capacity. Much faster. Much more reliable.
Just be sure to use the “Safely remove hardware” function after you create a Quicken Backup and before you unplug the USB device.

Let's just say that I'm writing comments for this Community, for users of all versions of Quicken on all versions of Windows, supported or not. I have fielded several comments over the years where users have created a backup to a USB memory stick, ripped it out as soon as the Quicken window closed, reformatted Windows, reinstalled Quicken and were utterly dismayed when their one and only backup file on the USB stick didn't work … because they had not waited long enough for Windows to finish writing the last batch of FAT file management I/Os.
Better safe than sorry. That's my advice.