In our ROMMELSBACHER blog you will find lots of helpful tips on making yoghurt.
Part 1: Basics & everything about milk
https://rommelsbacher.blog/2025/06/02/kleiner-joghurt-ratgeber-teil-1/
Part 2: Yoghurt bacteria & cultures
https://rommelsbacher.blog/2025/06/09/kleiner-joghurt-ratgeber-teil-2/
Part 3: Vegan alternatives & sour milk products
https://rommelsbacher.blog/2025/06/16/kleiner-joghurt-ratgeber-teil-3/
It is also important for the success of a successful yoghurt preparation that all equipment and ingredients are perfectly hygienic, as dairy products are very sensitive.
If the yoghurt does not set despite observing the above points, please check whether the appliance is reaching the correct temperature.