Error Caused by: java.lang.ClassNotFoundException: org.openqa.selenium.WebElement

Hi, i need a help.
We are trying to run a test suite on the KRE and it shows the following error. Someone help me.
Start reloading plugins…
Katalon version: 7.9.1
Plugin info URL: https://store.katalon.com/api/products/ks?appVersion=7.9.1&appType=ENGINE&licenseType=ENTERPRISE
Wed Apr 28 14:43:03 UTC 2021
java.lang.NoClassDefFoundError: org/openqa/selenium/WebElement
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2729)
at java.lang.Class.privateGetPublicMethods(Class.java:2930)
at java.lang.Class.getMethods(Class.java:1643)
at com.kms.katalon.custom.parser.NamingMethodVisitor.(NamingMethodVisitor.java:34)
at com.kms.katalon.custom.parser.CustomKeywordParser.parsePluginKeywords(CustomKeywordParser.java:135)
at com.kms.katalon.controller.KeywordController.parseCustomKeywordInStore(KeywordController.java:169)
at com.kms.katalon.controller.KeywordController.parseAllCustomKeywords(KeywordController.java:156)
at com.kms.katalon.activation.plugin.service.PluginService.refreshProjectClasspath(PluginService.java:402)
at com.kms.katalon.activation.plugin.service.PluginService.reloadPlugins(PluginService.java:231)
at com.kms.katalon.activation.plugin.handler.ConsoleModeReloadPluginsHandler.reload(ConsoleModeReloadPluginsHandler.java:22)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.kms.katalon.execution.console.ConsoleMain.reloadPlugins(ConsoleMain.java:391)
at com.kms.katalon.execution.console.ConsoleMain.launch(ConsoleMain.java:316)
at com.kms.katalon.console.application.ConsoleApplicationStarter.start(ConsoleApplicationStarter.java:37)
at com.kms.katalon.application.Application.runConsole(Application.java:125)
at com.kms.katalon.application.Application.start(Application.java:88)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:137)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:107)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:657)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
at org.eclipse.equinox.launcher.Main.run(Main.java:1447)
at org.eclipse.equinox.launcher.Main.main(Main.java:1420)
Caused by: java.lang.ClassNotFoundException: org.openqa.selenium.WebElement
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
at groovy.lang.GroovyClassLoader.loadClass(GroovyClassLoader.java:702)
at groovy.lang.GroovyClassLoader.loadClass(GroovyClassLoader.java:812)
at groovy.lang.GroovyClassLoader.loadClass(GroovyClassLoader.java:800)
… 33 more