New blank CD-R compatible w/OS9?

My sister has my old Mac which is running OS9. She wants to burn some files to a CD. She got some new, blank CD-R discs but the Mac spits them out when she loads them and pushes in the CD tray...they never even have a chance to show up on the desktop. Are newer CD-R's not compatible with older CD players/burners?

Are you sure its got a CD Burner? Very unlikely on a Mac of the age.
Now back then there was CD-R+ and CD-R- and that mattered with some drives.

Sorry, my memory going back 10 years gets a little bad. But the first thing I would confirm is that the drive does Burn.

Yeah, it's my old Mac from like 1998-2000. It was one of the first to have a CD rom drive, and I know I used to burn some of my early iTunes CDs on it. Not sure what the problem is...but she's inserted 3 different brands of blank CD-R and it spits them all out. Temperamental b**tard. Read that some old players won't take discs that can burn up to speeds of 32X, so that could possibly be it.