This issue has been ongoing for months/years.
A phone update essentially hides voicemail messages requiring a call into voicemail to retrieve. Enabling VisualVoiceMail fails to activate.
Revert phone app to prior version usually fixes the issue and restores partial operation: voicemails appear on the phone again, but VisualVoiceMail continues to try to activate and continues to fail. Allowing automatic updates - generally a good thing these days - gets a user right back to lost voicemails at random times.
Is there any update on if or when this issue will be corrected?