I have a ranking grid with the number of answers limited to 3 with a minimum of 1 response required to proceed. However, if a respondent only selected one answer, they are able to proceed even if their answer is not in the first column. Is there a way to prompt them to enter a single response in the 1st rank column?
There is no built-in function that would do this for your respondents. It is possible to write a custom script that would evaluate the answers to the ranking grid and tell your respondents that they failed to select a#1. The drawback to this is that the script would have to run on the page following the ranking grid question, requiring your respondents to hit the BACK button if they are interested in complying with your request.
My guess is that respondents think that they are clicking on a first choice but are somehow failing to make contact. We have seen occur during tests. I am not sure what you can do to prevent that. You might want to consider using the drag and drop ranking question type instead.