If it's a 554, set the bias spring on the ringer to the low physical resistance position (there are two positions).
Make sure that the ringer is wired with one side of each winding to the line, and the other wires to the capacitor position on the network.
The easiest way to do this is to find a drawing of the phone and wire it according to the drawing (normal).
Electrically, you have a winding lead to tip, the other to9 ring and a .47 uf capacitor in the middle. The capacitor is inside of the network unit in a 500/554.
The FIOS boxes and ATA's aren't great with mechanical ringers as a rule.
