An error might occur when exporting data only to Excel from a list, when the first field on the list is a Boolean type of field.
It occurs for any list that has an aggregation row configured.
STEPS TO REPRODUCE
This is being caused by Defect DE45701
CA PPM 15.5
CA PPM 15.5.1
The Defect DE45701 is fixed in 15.6
As a workaround on 15.5 and 15.5.1:
Move the Boolean field so that it is not the first column on the list.
Remove the aggregation row.