TestNG: All subsequent Test classes are skipped when @BeforeClass method fails?
This was a bug in Testng. solved in 6.9.5. Please upgrade.
Try to add @AfterClass(alwaysrun = true) or/and @AfterMethod(alwaysrun=true) as by default they are skipped if either BeforeClass or BeforeMethod are not completed.
The documentation on testNG Configuration Failures, Policy, and alwaysRun explains whether/when configuration failures cause listener methods (alwaysRun and other listeners) to be skipped, failure policies and best practices.