Why is STR_TO_DATE failing?

[KRISTY ATKINS]

I've got a query that returns the results below.
The field is a varchar.
The query is:
"SELECT answers.AnswerText
FROM answers INNER JOIN surveys ON answers.SurveyID = surveys.RecordID
WHERE answers.AnswerText IS NOT NULL AND answers.QuestionID = 116"

If I change the query to the sql below it returns all NULL values except the one having the value 06/12/1992 10:00:00.

"SELECT STR_TO_DATE(answers.AnswerText, '%m/%d/%Y %h:%i:%s')
FROM answers INNER JOIN surveys ON answers.SurveyID = surveys.RecordID
WHERE answers.AnswerText IS NOT NULL AND answers.QuestionID = 116"

Why is mysql returrning NULL instead of the datetime?
Is there anything I can do to fix this problem?


05/07/1977 00:00:00
06/14/1989 21:00:00
12/22/1995 20:00:00
09/12/1991 00:00:00
04/01/2003 00:00:00
03/15/2014 00:00:00
03/17/2002 21:30:00
10/24/2008 00:00:00
03/12/1975 21:00:00
09/20/2016 21:30:00
04/12/1981 22:00:00
06/12/1992 10:00:00
09/04/2004 22:00:00
06/12/2005 00:00:00
12/25/2019 19:00:00
03/05/1974 13:00:00
04/16/2011 22:00:00
10/09/1998 21:00:00
04/27/1984 16:00:00