If you have a prepaid number, you can only sync contacts.
Ensure your Verizon Cloud app is up to date as the following steps apply to the most recent version.
Drag the switches left or right to enable/disable Backup settings.
Enabled when in the green position.
Drag the switches left or right to enable/disable the Background Upload setting.
The Background Upload setting is enabled when the switch is green.
From the How to Back Up section, select the network option:
Selected when a check mark is present.