These are just guesses…maybe they'll help.
OS9 will recognize a standard Red Book CD in the internal ATAPI CD drive. It will appear in a finder window with listings "Track 1, Track 2" etc.
Over USB, different stuff has to happen.
*There are USB extensions that must be enabled:
"Audio CD Access" 5.3.4 This is specifically for music CDs
"Foreign File Access" 5.3.3 This MUST be enabled for the Audio CD Access to work
"USB Authoring Support" 1.1.2 For USB CD-R and CD-RW Maybe necessary, maybe not.
If the CD does NOT appear upon insertion, it's because the OS doesn't know what to do with what the USB drive told it.
(If you can play a DVD, I'll bet that the DVD player launches itself upon insertion)
You need a default app to play a pre-recorded CD as well. That will either be iTunes or "Apple CD Audio Player". Both have autoplay selections in their prefs
BUT (big BUT) It's possible they don't recognize the info coming from the USB CD drive so they don't do anything.
Remember, when you stick a CD into the USB drive, it simply sends a data burst to the OS saying "I'm here with these certain type of files" - The OS has to then know what to do with them, so you probably need an app to respond and launch.
Meanwhile…
Toast has three USB extensions that must be in the Toast/Extensions folder. "USB Support" "USB Support B" "USB Support C" See if they're there.
*There may be an issue if the drive expects USB2 burn operation.
* You should have/use the last Toast 5 - that is "Toast Titanium" 5.1.2
That should keep you busy for a little while…
Holla back.