That’s unlikely to help - the screenshot shows a solid 0°C came in 41 s ago from the emonTH, so the problem is the emonTH isn’t seeing and reading the sensor.
The value that’s transmitted is initialised to zero when you put the batteries in and the software starts up. It searches for sensors and if it doesn’t see one, that value stays at zero. You’re seeing exactly that.
You’ve definitely got it connected like this? https://wiki.openenergymonitor.org/index.php/EmonTH_V1.5#External_DS18B20_Temperature_Sensor_Connections
And the hopefully stupid question: the wires are stripped back far enough?
(I ask because I once spent half a day finding a fault which was exactly that - done by a professional wireman.)
Does the LED come on for 5 s when you put the batteries in, then go out?
If you have a programmer, plug that in and see what the monitor shows at power-up. Or if you’ve got a multimeter, measure across the red and black wires (3 & 6). You should see about 3.3 V for a very brief moment at power-up, then every time it tries to read the sensor (i.e. about every 55 s).
If it still refuses to cooperate or you aren’t able to check anything else, then I suggest emailing the Shop [email protected] and link to this thread.