Voicemail message is expired after certain days. It wouldn't stay there forever. If you would like to keep it, you have to re-save it regularly or use visual voicemail to download the message.

I am Not sure if Koodo had still had those voicemails or not, you can try to schedule a callback and ask a rep to look into it.

Thanks for your response, Dinh!  Yes, I regularly save my vm msgs.  This isn’t the first time this has happened with Koodo.  I did schedule a callback with Koodo to see if these vm msgs can be retrieved.