As others have said I quite certain it won’t play mp3 files.
A top tip if you are just burning/copying a normal audio cd is to buy blank cd’s that bear the DIGITAL AUDIO symbol. These are geared specifically to music recording and are much more compatible with older cd players. Example disks at amazon:
MAXELL DIGITAL AUDIO XL-II 80 BLANK MUSIC CD-R - 50 DISCS
https://www.amazon.co.uk/dp/B008TPQW..._Mt.JCb7C1E2QV