Phone Line Elevator

We have a bit of an issue on a residential project. Client has Verizon Fiber Ont and the Verizon tech told us that when only Fiber is hooked up the phone jack on the ONT isn't strong enough to push dial tone. He mentioned some sort of phone line booster most people use but I can't find anything. We have Cat6 running from ONT to the elevator panel. Anyone know what he could be talking about.

I also know people are using cellular modules instead of a dedicated phone line for elevators. If anyone has recommendations it'd be appreciated.

Edit : Problem solved. The Fiber ONT POTS worked. I went into the mechanical room and the elevator contractor used a 4 conductor (green & white) to splice onto our phone line and red and black to hook up to the elevator board. Fixed that and should have no issues for inspection.