Unit Tests with TESTNG in Maven

I am developing unit tests with the TESTNG framework and I have encountered a problem when obtaining the coverage report.

Steps:

• I launch the Maven project.

  clean org.jacoco:jacoco-maven-plugin:prepare-agent install
  

• The execution ends but the coverage report is not generated.

• The file Target->coverage-reports is created in the folder jacoco-ut.exec of the project.

• The coverage of the unit tests does not appear.

The file has 80.1KB, but does not show the reflected coverage .

How can I solve this problem?