Can't seem to get MQTT data to populate in sitemap

So on my setup (3.2.0 on RPi) I’ve got Mosquitto setup and running nicely and I can see in it’s logs that Openhab is connecting just fine. I can verify that my several ESP8266’s are sending data and I can confirm it with testing via the command line mosquitto_sub tool from a remote system. So data is definitely flowing into the system. For reference i am using the PubSubClient and the publish code looks like this:

    // Publishes Temperature and Humidity values
    static char temperatureTemp[6];
    dtostrf(f, 6, 1, temperatureTemp);
    
    static char humidityTemp[6];
    dtostrf(h, 6, 1, humidityTemp);
    
    client.publish("sensors/frontroom/temperature", temperatureTemp);
    client.publish("sensors/frontroom/humidity", humidityTemp);

The problem I’m having is how to get that out into my sitemap. I started by following the tutorial and I created the MQTT Broker. Then I created a Generic MQTT Thing based on the broker:

Then in the generic MQTT Think I created a channel for the topic:

and lastly I created the point item that is linked to that channel.

So I have two issues. When I try to load the sitemap with the data:

Text item=FrontroomTemp label="Frontroom [%.1f °F]"

the mobil app just says “Err” and the logfiles show:

2022-03-31 20:19:12.658 [WARN ] [ui.internal.items.ItemUIRegistryImpl] - Exception while formatting value '' of item FrontroomTemp with format '%.1f °F': f != java.lang.String

I’m not exactly sure what I am doing wrong here. For some reason it seems to be getting a null or zero length string from the topic.

Do it with type Number

Sorry, do what with type Number where?

The sitemap entry that I have is directly out of the demo documentation.

*edit: I see what you mean. Change the item type to Number. Ok let me tweak that and see.

exactly. I have it as Number defined (item and channel).

Also I use MQTT Spy which helps a lot. So you have a graphical tool to sniff on the MQTT traffic. It also acts as a client to send some test values.