As voicemail is a carrier feature, I would recommend reaching out to your carrier for further assistance.
Be sure to click " ✓ Accept as Solution" when you find an answer that works for you.
Please note, notification emails are a DO NOT REPLY address, you must log-in on the community page in order to respond.
That was it! I use AdGuard and it apparently was breaking Voicemail, in addition to making reservations through Google Maps.
Fortunately AdGuard can be disabled per app. Now Voicemail and Maps both work flawlessly.