There are a few tricks to getting yoghurt to set and it is really all solved with good hygiene and controlling the temperature. Oh and allowing time for nature to do its thing.
HINT … I use my Thermomix to mix and heat the mixture but you could use the internal pot and induction cook top to heat your milk mixture while stirring to ensure even heating. If you want to use fresh milk, the process is a little more complicated and time consuming than if using UHT milk. I prefer to use UHT as it is very quick and eliminates having to heat sterilise the milk yourself.