It is possible that a particular comparison does not yield any statistically significant differences. When this is the case, you will be presented with a message in the comparison explorer as shown below.
There are three primary reasons this might occur:
There is a large amount of overlap between data sets, and thus no statistically significant differences exist.
One or both of the data sets are too small to retrieve differences that are statistically significant.
There is an issue with your uploaded data that caused an error in the analysis process.