This article is for pre-2022 Odlo's I-Thermic baselayers and midlayers only.
Option #1: through the app
Open your clim8® app and go to product settings to reset the batteries.
Option #2: on the product
Make sure the battery is turned off and the app is killed on your phone.
For baselayers/midlayers: snap the module on the shirt. Press the power button during 7 seconds until the LED indicator bliss.