No valid coverage data available - Rcov report- Jenkins

No valid coverage data available
Tracking and trending code coverage works best when like is compared with like. In this regard it is best to only track builds when all unit tests are passing.
This plugin will not report code coverage until there is at least one stable build.

this message is shown when i run a rails project in jenkins and in post build action set publish rcov report
report is generated under workspace/coverage.rcov/index.html

whats the solution ?

thanks in advance