I tried to use the Summarize Within tool on some dummy data but got no output. In trying to understand what I was doing incorrectly I found this tutorial and tried that but with the same problem - it runs without any errors - indicates that the function has run but the output feature class is not created. Could it be a license issue - where the function runs but doesn't allow access to the output feature class?
There are some bugs, for example....
BUG-000134787: The Summarize Within tool is not performing when usi.. (esri.com)
and you can look at more to see if any meet your case