A TAMB is designed to be connected to a Loop Start or Ground Start Trunk, OR a RINGING analog station port (or Centrex telephone line).
If you use an analog port configured as Standard or IVR, calling the extension number is going to ring once, then the TAMB will answer, and connect the audio on the analog station port to the audio input of the amplifier
An analog station port on an IP Office programmed as a paging port does not ring, it simply has audio or not on it. The TAMB does not have an option for this, so try removing the TAMB from the equation all together. Connect the Tip and Ring of the analog station port to the input of the amplifier, program the analog station port as a paging port, and use a short code for Dial Paging to the extension number of the station port.