Verizon is required by tariff (law) to provide enough current and voltage to ring an equivalent of 5.0A.
Count your RE and if it's less than 5.0 you have case.
A typical 500-type set (or 2500) is 1.0A. newer electronic ringers are listed at less than 1.0A.
If that number of ringer equivalence exceeds the capability of your landline, you can complain, and they are obligated to fix the problem.
