Without installing a custom device handler (also known as “DTH” or “DH”), messages from Xiaomi devices may or may not be interpreted correctly, which means you’re missing out on either partial or complete functionality, and correct display for the device in the SmartThings Classic mobile app.
There’s a very thorough FAQ on installing custom Device Handler or Smart App code here:
In a nutshell, you need to
copy the text of the code for the Aqara Temp/Humidity Sensor DTH from here
Create a new Device Handler in the IDE for your ST hub and choose the “From code” option
Paste in that code you copied in step 1
Click Create, and then Publish
After that, when pairing your sensor, your SmartThings hub will use “fingerprint” information contained in the DTH to match up and assign the custom DTH to your Aqara Temp/Humidity sensor. If for some reason that doesn’t happen, the custom DTH can also be manually assigned (discussed repeatedly in this forum thread.)
This is completely normal behavior for the Xiaomi sensors. To conserve battery, they only report temperature / humidity when either has changed beyond a minimum threshold, rather than reporting every X minutes.
There are loads of great smart devices which require the “hoop-jumping” of installing custom DTHs or Smart Apps to work properly or work well with SmartThings, so it’s a shame to miss out on all of that. But I can understand wanting the achieve the promise of simplicity that Samsung’s and other device manufacturer’s marketing portrays.
I’d suggest a search of the forums here for an “accurate” temperature / humidity sensor. Or start a new thread asking about it. In a quick search I only found this:
…and unfortunately the Fibaro FGK-101 “Door/Window & Temperature Sensor” w/ optional DS18B20 that the last poster recommends does require a custom DTH…