Virtual Agent shows a blank pageIssue While loading the "Virtual Agent" (VA) client via "Service Portal" or via direct VA client url (/$sn-va-web-client-app.do?sysparm_nostack=true&sysparm_stack=no), blank screen was rendering forever as shown in the below screenshot, The network tab shows the following REST API request "https://<InstanceName>.service-now.com/api/now/v2/cs/session" is failing with below error, error: {message: "java.lang.NoClassDefFoundError: javax/ws/rs/core/Response$StatusType",…}detail: "javax/ws/rs/core/Response$StatusType Check logs for error trace or enable glide.rest.debug property to verify REST request processing"message: "java.lang.NoClassDefFoundError: javax/ws/rs/core/Response$StatusType"status: "failure" At the same time Looking into the session debug (or node log) of the failing request could see below errors, 11:43:41.564: [Context] TopicName: system TopicId: xxxxxxxxxxxxxxxxxxxxxxxxx [MessageServiceImpl] java.lang.NullPointerException: Error occured when processing message: no thrown errorlog11:43:41.565: Error while creating Session: java.lang.NullPointerException: com.glide.cs.qlue.module.coma.MessageServiceImpl.handleError(MessageServiceImpl.java:457) com.glide.cs.qlue.module.coma.MessageServiceImpl.receiveMesage(MessageServiceImpl.java:209) com.glide.cs.qlue.module.coma.SilentHandshake.createSystemConversation(SilentHandshake.java:117) com.glide.cs.qlue.module.coma.SilentHandshake.process(SilentHandshake.java:80) com.glide.cs.qlue.module.coma.SessionServiceImpl.createSessionV2(SessionServiceImpl.java:58) com.glide.cs.qlue.module.coma.SessionResourceV2.createSession(SessionResourceV2.java:42) sun.reflect.GeneratedMethodAccessor10455.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) java.lang.reflect.Method.invoke(Method.java:498) com.glide.rest.handler.impl.ServiceHandlerImpl.invokeService(ServiceHandlerImpl.java:44) com.glide.rest.processors.RESTAPIProcessor.process(RESTAPIProcessor.java:290) com.glide.processors.AProcessor.runProcessor(AProcessor.java:531) com.glide.processors.AProcessor.processTransaction(AProcessor.java:229) com.glide.processors.ProcessorRegistry.process0(ProcessorRegistry.java:188) com.glide.processors.ProcessorRegistry.process(ProcessorRegistry.java:177) com.glide.ui.GlideServletTransaction.process(GlideServletTransaction.java:31) com.glide.sys.Transaction.run(Transaction.java:2147) java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) java.lang.Thread.run(Thread.java:748)log11:43:41.673: java.lang.NoClassDefFoundError: javax/ws/rs/core/Response$StatusType: com.glide.rest.util.RESTRuntimeException: java.lang.NoClassDefFoundError: javax/ws/rs/core/Response$StatusType: com.glide.rest.handler.impl.ServiceHandlerImpl.handleInvocationTargetException(ServiceHandlerImpl.java:76) com.glide.rest.handler.impl.ServiceHandlerImpl.invokeService(ServiceHandlerImpl.java:49) com.glide.rest.processors.RESTAPIProcessor.process(RESTAPIProcessor.java:290) com.glide.processors.AProcessor.runProcessor(AProcessor.java:531) com.glide.processors.AProcessor.processTransaction(AProcessor.java:229) com.glide.processors.ProcessorRegistry.process0(ProcessorRegistry.java:188) com.glide.processors.ProcessorRegistry.process(ProcessorRegistry.java:177) com.glide.ui.GlideServletTransaction.process(GlideServletTransaction.java:31) com.glide.sys.Transaction.run(Transaction.java:2147) java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) java.lang.Thread.run(Thread.java:748)log11:43:41.673: #4197340 [REST API] RESTAPIProcessor : Handling exception java.lang.NoClassDefFoundError: javax/ws/rs/core/Response$StatusTypelog11:43:41.673: #4197340 [REST API] RESTAPIProcessor : Unknown exception RESTRuntimeException:java.lang.NoClassDefFoundError: javax/ws/rs/core/Response$StatusTypeDetail: javax/ws/rs/core/Response$StatusTypelog11:43:41.674: *** End #4197340 /api/now/v2/cs/session, user: antony.xavier@snc, total time: 0:00:00.404, processing time: 0:00:00.404, SQL time: 0:00:00.117 (count: 36), source: 37.98.232.61 , type:rest, method:POST, api_name:now/cs, resource:now/v2/cs/session, version:v2, user_id:antony.xavier@snc, response_status:500 ReleaseMadrid and the above releases.CauseFollowing are the possible causes which can manifest the above-described symptoms, The initial messages are missing due to the issue with activating the "Conversation General Settings" plugin (id=com.glide.cs.settings) The users involved in the chat are assigned with snc_read_only role Some of the system topics(sys_cs_topic with "Is System Topic" column set as true) were deleted by the admin user Setting the vendor field as empty on the system topicResolutionBased on the cause, do the following corrective action to resolve the issue, For the issue with the "Conversation General Settings" plugin, repair the pluginMake sure the users involved in the chat are not assigned with snc_read_only role If the system topics were deleted, import them from another working instance Make sure the vendor field is not empty on the system topic