How can helper be unavailable?

TL;DR
When I call the service to press a helper button I get an error:

[homeassistant.helpers.service] Referenced entities input_button.door_camera_alarm are missing or not currently available

Context:
I am using Frigate NVR with home assistant’s Lovelace integration. The camera I am using has a native sound out and I am using a curl shell script to sound the alarm. To trigger the shell script I created a helper button and automation that calls the script if the button is pressed.
In the card however I am suing a service to call a button press action:

      - type: custom:frigate-card-menu-icon
        title: Alarm
        icon: mdi:bullhorn
        entity: input_button.door_camera_alarm
        tap_action:
          action: call-service
          service: button.press
          service_data:
            entity_id: input_button.door_camera_alarm

Every part works individually… except then I call a service to press the button. (If I press the button in the helper it works fine too)

An input_button is not a button.

Try input_button.press

Instead of what? Which line?
Also, I know that is why I call button.press service and does ‘press’?