Hi Heaven Clacken,
The microflow you are trying to set up is an onchange microflow which should be triggered from the screen you created in the before step of your training. So this Microflow should be configured like this,
in this case the microflow you created should have an input parameter TrainingEvent. Check whether you configured this microflow in the onchange then check the microflow has TrainingEvent object as input parameter.
The issue is the Microflow dont have the input parameter now.