try to ensure that date is in format YYYY-MM-DD.
The best way would be to change published format (tbh I have no idea why it’s published in local format). If impossible then you probably have to use template mqtt sensor to reparse incomming date value
After removing the line for device_class, I am still getting “unknown” for the sensor (after a restart). So seems like the main issue here is importing the value “03/17/2022” into the state.
can you express the mqtt the way mqtt explorer does e.g.
{“message”:{“id”:107,“channel”:0,“battery”:1,“temperature”:7.3,“humidity”:76},“protocol”:“nexus”,“length”:“107”,“value”:“107”,“repeats”:2,“status”:2}
It might give a clue how to extract the date using a value template.
The screenshot of MQTT Explorer shows that the payload published to ecowater/out_of_salt is not a retained message (i.e. it’s not stored on the MQTT Broker). That means every time you modify the sensor’s YAML configuration and execute Reload MQTT Entities, the newly revised MQTT Sensor gets no value from the broker and so it reports unknown. It must wait until the source of the data publishes another payload to ecowater/out_of_salt in order to receive it.
How often does the data’s source publish a new payload to ecowater/out_of_salt?