When clicking on a row (or pressing ctrl+a) within the results of an aggregate report the row is briefly selected and then almost instantly deselected. With JMeter 2.13 selection was persisted and I could copy the results. Tested on JMeter 4.0 r1823414 on Windows 7 64-bit with 64-bit JRE 1.8.0_151 and Windows 10 64-bit with 64-bit JRE 1.8.0_171
Should be fixed in nightly. It would be great, if you could confirm the fix works for you, too. *** This bug has been marked as a duplicate of bug 62097 ***