Zend Stuidio 9 Unable to read repository

[radici]

Some sites could not be found. See the error log for more detail.
Unable to read repository at packagist dot org/packages/zendframework/zendframework/content.xml.
sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification