Questionnaire Properties - Trainers Tips
Anytime you select Reduce All as an option you must meet the following conditions:
The question needs to be in its own section with no other questions
The section can be weighted however you would like – even 0%
Question weighting must be 100% as it is the only question in the section
If these 3 conditions are not met, the system will show an error message.
For more details refer to the documentation - Setting Questionnaire Properties