Problems with messages with sum of states

Your float() functions need a default… if you check your logs, you will likely see an error message.

alias: Sprachansage Fahrt Abfahrt im Geschäft
description: ''
trigger:
  - platform: state
    entity_id:
      - person.manuel
    from: Brütsch/Rüegger
    to: not_home
condition: []
action:
  - variables:
      message: >
        Ich fahre jetzt im Geschäft los. Aktuelle Ankunftszeit  {{
        (now() | as_timestamp + 
        float(states('sensor.fahrt_1'), 0)  +
        float(states('sensor.fahrt_2'), 0)  +
        float(states('sensor.fahrt_3'), 0)  +
        float(states('sensor.fahrt_4'), 0) )
        | timestamp_custom("%H:%M", True) }} Uhr
  - service: script.alexa_sprachausgabe_og_komlett
    data:
      message: '{{message}}'
      type: announce
  - service: notify.telegram_manuel
    data:
      title: Info!
      message: '{{message}}'
mode: single