Hi @mytruong,
Please download Katalon Studio v6.1.2 release: https://github.com/katalon-studio/katalon-studio/releases and open a project with embedded the katalon-studio-ashot-plugin.jar, you will see the original error on Event Log tab:
Caused by: java.lang.NoClassDefFoundError: Unable to load class kms.turing.katalon.plugins.visualtesting.ScreenCapture due to missing dependency ru/yandex/qatools/ashot/Screenshot
at org.codehaus.groovy.vmplugin.v5.Java5.configureClassNode(Java5.java:421)
at org.codehaus.groovy.ast.ClassNode.lazyClassInit(ClassNode.java:357)
at org.codehaus.groovy.ast.ClassNode.getMethods(ClassNode.java:479)
at com.kms.katalon.custom.parser.CustomKeywordParser.parsePluginKeywords(CustomKeywordParser.java:130)
at com.kms.katalon.controller.KeywordController.parseCustomKeywordInPluginDirectory(KeywordController.java:187)
at com.kms.katalon.controller.KeywordController.parseAllCustomKeywords(KeywordController.java:137)
at com.kms.katalon.controller.ProjectController.openProjectForUI(ProjectController.java:95)
at com.kms.katalon.composer.project.handlers.OpenProjectHandler$1.run(OpenProjectHandler.java:152)
at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:119)
To resolve this error, your custom keyword plugin needs to package along with the ashot.jar. Please read this article for more details: How to resolve external dependencies for a Plugin