mqtt_volumeknob.yaml

blueprint:
    name: Mqtt-VolumeKnob
    description: Using the (Tuya ERS-10TZBVK-AA) MQTT Volume-Knob to controle the volume of a primary MediaPlaye (with 2nd option on hold & rotate)
    domain: automation
    input:
      primary_media:
        name: Primary Player
        description: Media Player for main volume control
        selector:
          entity:
            filter:
              domain: media_player
      secondary_media:
        name: Secondary Player
        description: an additional Media Player object for the push&rotate function
        selector:
          entity:
            filter:
              domain: media_player
      volume_knob:
        name: Volume Knob
        description: the (Tuya) MQTT device with the rotation for controling volume
        selector:
          entity:
            filter:
              integration: mqtt
              domain: sensor
alias: Mqtt-VolumeKnob
mode: queued
max: 10
trigger:
  - platform: state
    entity_id:
      - !input volume_knob
condition: []
variables:
  p_media: !input 'primary_media'
  s_media: !input 'secondary_media'
action:
  - variables:
      action: >-
        {{ trigger.to_state.attributes.action }}
      volume_entity: !input primary_media
  - choose:
      - conditions:
          - >-
            {{ action == "brightness_step_down" }}
        sequence:
          - service: media_player.volume_set
            data_template:
              entity_id: !input primary_media
              volume_level: >-
                {{ state_attr(p_media,'volume_level')  -
                ((trigger.to_state.attributes.action_step_size / 19) | round
                )/100 }}
      - conditions:
          - >-
            {{ action == "brightness_step_up" }}
        sequence:
          - service: media_player.volume_set
            data_template:
              entity_id: !input primary_media
              volume_level: >-
                {{ state_attr(p_media,'volume_level')  +
                ((trigger.to_state.attributes.action_step_size / 19) | round
                )/100 }}
      - conditions:
          - >-
            {{ action == "color_temperature_step_up" }}
        sequence:
          - service: media_player.volume_set
            data_template:
              entity_id: !input secondary_media
              volume_level: >-
                {{ state_attr(s_media,'volume_level')  +
                ((trigger.to_state.attributes.action_step_size / 19) | round
                )/100 }}
      - conditions:
          - >-
            {{ action == "color_temperature_step_down" }}
        sequence:
          - service: media_player.volume_set
            data_template:
              entity_id: !input secondary_media
              volume_level: >-
                {{ state_attr(s_media,'volume_level')  -
                ((trigger.to_state.attributes.action_step_size / 19) | round
                )/100 }}

Removed the 'test' from the alias and name, added the specific volume knob mode (ERS-10TZBVK-AA)