Why am I not getting any voicemail messages

Which phone are you using? And when you check, are you dialing into voicemail (1 + your area code + your number) or tapping the visual voicemail in the phone app?

If it's an iPhone, check whether Apple Live Voicemail is turned on, some customers do have problems with their Koodo voicemail when it is. As well, log in to Self Serve, go to Mobile Services and Manage add-ons and see if Voicemail to Text is on the line. With that one you get the transcribed message as a text or email instead of a voicemail notification.

I would also reset the network settings and restart the phone, then have someone leave you a test message and dial in to check.

Koodo's voicemail page is here https://www.koodomobile.com/en/help/voicemail