BrowserNotOpenedException: Browser is not opened Build info:

I get the exception below while running test in chrome and firefox headless. Any idea why?

com.kms.katalon.core.webui.exception.BrowserNotOpenedException: Browser is not opened
Build info: version: ‘3.141.59’, revision: ‘e82be7d358’, time: ‘2018-11-14T08:25:53’
System info: host: ‘EWR-DBMONITOR-0’, ip: ‘10.50.34.71’, os.name: ‘Windows Server 2016’, os.arch: ‘amd64’, os.version: ‘10.0’, java.version: ‘1.8.0_181’
Driver info: driver.version: unknown
at com.kms.katalon.core.webui.driver.DriverFactory.verifyWebDriverIsOpen(DriverFactory.java:892)
at com.kms.katalon.core.webui.driver.DriverFactory.verifyWebDriver(DriverFactory.java:877)
at com.kms.katalon.core.webui.driver.DriverFactory.getWebDriver(DriverFactory.java:863)
at com.kms.katalon.core.webui.driver.DriverFactory$getWebDriver$0.call(Unknown Source)
at customPackage.premium.premiumcheck(premium.groovy:181)
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.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1215)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1024)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:812)
at groovy.lang.DelegatingMetaClass.invokeMethod(DelegatingMetaClass.java:144)
at customPackage.premium.invokeMethod(premium.groovy)
at com.kms.katalon.core.main.CustomKeywordDelegatingMetaClass.invokeStaticMethod(CustomKeywordDelegatingMetaClass.java:50)
at org.codehaus.groovy.runtime.callsite.StaticMetaClassSite.call(StaticMetaClassSite.java:53)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:117)
at Script1595327687603.run(Script1595327687603.groovy:29)
at com.kms.katalon.core.main.ScriptEngine.run(ScriptEngine.java:194)
at com.kms.katalon.core.main.ScriptEngine.runScriptAsRawText(ScriptEngine.java:119)
at com.kms.katalon.core.main.TestCaseExecutor.runScript(TestCaseExecutor.java:337)
at com.kms.katalon.core.main.TestCaseExecutor.doExecute(TestCaseExecutor.java:328)
at com.kms.katalon.core.main.TestCaseExecutor.processExecutionPhase(TestCaseExecutor.java:307)
at com.kms.katalon.core.main.TestCaseExecutor.accessMainPhase(TestCaseExecutor.java:299)
at com.kms.katalon.core.main.TestCaseExecutor.execute(TestCaseExecutor.java:233)
at com.kms.katalon.core.main.TestCaseMain.runTestCase(TestCaseMain.java:114)
at com.kms.katalon.core.keyword.builtin.CallTestCaseKeyword$_callTestCase_closure1.doCall(CallTestCaseKeyword.groovy:59)
at com.kms.katalon.core.keyword.builtin.CallTestCaseKeyword$_callTestCase_closure1.call(CallTestCaseKeyword.groovy)
at com.kms.katalon.core.keyword.internal.KeywordMain.runKeyword(KeywordMain.groovy:68)
at com.kms.katalon.core.keyword.builtin.CallTestCaseKeyword.callTestCase(CallTestCaseKeyword.groovy:81)
at com.kms.katalon.core.keyword.builtin.CallTestCaseKeyword.execute(CallTestCaseKeyword.groovy:44)
at com.kms.katalon.core.keyword.internal.KeywordExecutor.executeKeywordForPlatform(KeywordExecutor.groovy:72)
at com.kms.katalon.core.keyword.BuiltinKeywords.callTestCase(BuiltinKeywords.groovy:334)
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.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeStaticMethod(MetaClassImpl.java:1469)
at org.codehaus.groovy.runtime.callsite.StaticMetaClassSite.call(StaticMetaClassSite.java:53)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:141)
at daily.Testcall8(daily.groovy:86)
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.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:108)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:661)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:869)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1193)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:126)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)