The vertical scale of the coverage graph is too small, so the "lineCovered" graph is not rendered (see attachment).
May be related to JENKINS-15177
I think I'm suffering from the same issue. Here is the link https://reference.ci.cloudbees.com/view/gradle/job/1%20-%20snapshot-gradle/lastBuild/jacoco/
You can see that there was "lineCovered" initially, but then it disappears. Line disappeared after I've fixes "classes" folder location, previously it was pointing to 2 locations - main and test classes.
version 1.0.9 fixes it