Unreadable CD-R. How to fix?

I recently came across CD-Rs that I'd stored old photos on from around 2005/6. My partner was super excited as we think the CDs include photos that we thought we'd lost when a backup drive failed.

I plugged an old drive and CD into my M3 mac (running Sonoma 14.3.1), crossed my fingers and hoped that it would read. It doesn't. The good news is that it recognises the drive, but it doesn't see the CD as readable. Any ideas how I can access these files. When I plug in the drive, I get a pop up window and the message "The disk you attached was not readable by this computer" with two option buttons, Ignore or Eject.

My Finder settings allow for CDs. Can anyone suggest possible workarounds?! Thanks in advance for any help!