Unable to change MQTT Post to Retain

Configuration
1

I created some MQ posts with retain=false. After testing I decided to make some to be retained and set the retain flag to true. Despite reloading the YAML, reloading HA and even rebooting, the posts are not being retained. I’m not sure what the issue is. I have other posts that are being retained - also created in YAML. I am long term user of MQTT although a somewhat new user of HA. The Mosquito server is on a separate Linux box on the same sub-net and is problem free. The webhook is forwarded by Nebu Casa and is properly formatted. Here is a portion of the YAML definition - the full definition is much larger but just repeats this pattern. Suggestions appreciated.

- id: "mh_environment_refresh"
  alias: MH Environment Refresh
  description: "Webhook from MH with temp/hum values"
  trigger:
    - platform: webhook
      allowed_methods:
        - POST
        - PUT
      local_only: false
      webhook_id: <hidden>
  action:
    - service: mqtt.publish
      data:
        qos: 0
        retain: true
        topic: Motorhome/Environment/Coach
        payload: "{{ trigger.json.environment.CoachTemp }}"
    - service: mqtt.publish
      data:
        qos: 0
        retain: true
        topic: Motorhome/Environment/Hum
        payload: "{{ trigger.json.environment.CoachHum }}"
2

Surprised at this. Setting retain true (after false) should work, and does in my experience. Is it possible any existing code remains?

What broker is this?

As maybe a solution delete the topic/payload with say MQTT Explorer and let it be recreated.

Also just in case this is misleading you the ‘retained’ tag advised by MQTT Explorer does not show if the topic is posted retained or not. It shows instead if the current value displayed was a retained value at connection or is a newer updated value since connection of the client. That fooled me too.

3

Using MQTT Explorer on Mac/OS - your explanation of the RETAIN flag not showing unless it was a retained value at startup was the answer. Restarting Explorer showed the flag. Tricky! Thanks!