BLE Example - Notify/Indicate operations not sending updated data

I’m using the Mbed OS example (here https://github.com/ARMmbed/mbed-os-example-ble/tree/master/BLE_GattServer) on a Cypress PSoC6 chip. When I use the recommended LightBlue app on my iPhone, I can see the request for notifications get sent/received by the device, but Mbed OS never actually sends the notifications that the data has changed.