2015 Macbook Pro. External USB Superdrive. Could not burn CD-R from Garageband. Blank CD is very old, wrong format?

Old CDs are very unreliable. Heat, dust, anything that might get ingrained in the wax substrata can defeat the longevity of the disc. Unless you kept them in a cool place inside a jewelbox that is kept clean, I would not count on them.

Media manufacturer does make a difference too. Sony, Taiyo, Verbatim, Imation are the better media companies.

Anything prepackaged in a spindle can easily get scratched by the disc stored below it.

Do not write anything on the physical disc itself in terms of markers, stickies, and use the jewelbox inserts to identify the disc, and keep out one disc at a time.