I am subscribed to the Visual Voicemail version 18.104.22.168864 feature on my T-Mobile account on the Samsung Galaxy S8 running Oreo version 8.0.0. Most of the time, it fails to synchronize my messages to the app. I get a message that says it failed to synchronize messages and to make sure I am connected to the data network. This is happening whether WiFi is on or off and I'm never in an area where I am not well covered by the T-Mobile network. This is very annoying because I use my phone for business as well as personal calls and I need Visual Voicemail to work consistently!
I have uninstalled and reinstalled the app and cleared the data cache several times already.
Best answer by tmo_amandaView original