MSGraph Email Poller

2021-08-09 17:50:26,625 [Appian Work Item - 0 - execution00 : UnattendedJavaActivityRequest] DEBUG com.appiancorp.ps.msgraphmail.MSGraphMailPollerSmartServic e - Connecting to MS Graph authentication provider
2021-08-09 17:50:26,863 [Appian Work Item - 0 - execution00 : UnattendedJavaActivityRequest] ERROR com.appiancorp.ps.msgraphmail.MSGraphMailPollerSmartServic e - Unexpected error polling for mail
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:357)
at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1908)
at com.appiancorp.ps.msgraphmail.MSGraphConnector.<init>(MSGraphConnector.java:75)
at com.appiancorp.ps.msgraphmail.MSGraphMailPollerSmartService.run(MSGraphMailPollerSmartService.java:171)
at com.appiancorp.process.runtime.framework.DefaultActivityExecutor$1.lambda$call$0(DefaultActivityExecutor.java:131)
at com.appiancorp.plugins.PluginUsageLogger.runWithPluginInformation(PluginUsageLogger.java:52)
at com.appiancorp.process.runtime.framework.DefaultActivityExecutor$1.call(DefaultActivityExecutor.java:131)
at com.appiancorp.process.runtime.framework.DefaultActivityExecutor$1.call(DefaultActivityExecutor.java:125)
at com.appiancorp.common.ContextClassLoaderSwitcher.runInContext(ContextClassLoaderSwitcher.java:25)
at com.appiancorp.process.runtime.framework.DefaultActivityExecutor.execute(DefaultActivityExecutor.java:125)
at com.appiancorp.process.engine.UnattendedJavaActivityRequest.execute(UnattendedJavaActivityRequest.java:88)
at com.appiancorp.process.engine.UnattendedJavaActivityRequestResponseCreator.getJavaActivityResultResponse(UnattendedJavaActivityRequestResponseCrea tor.java:21)
at com.appiancorp.process.engine.UnattendedJavaActivityRequest.getJavaActivityResultResponse(UnattendedJavaActivityRequest.java:67)
at com.appiancorp.process.engine.UnattendedJavaActivityRequest.execute0(UnattendedJavaActivityRequest.java:55)
at com.appiancorp.process.engine.ContinuationRequest.executeOuter(ContinuationRequest.java:73)
at com.appiancorp.process.engine.ContinuationRequest.execute(ContinuationRequest.java:102)
at com.appiancorp.process.workpoller.UnattendedRequestHandlerBean.onMessage(UnattendedRequestHandlerBean.java:36)
at com.appiancorp.process.workpoller.WorkItem.run(WorkItem.java:93)
at org.springframework.jca.work.SimpleTaskWorkManager$DelegatingWorkAdapter.run(SimpleTaskWorkManager.java:239)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
at com.microsoft.aad.msal4j.AuthenticationResultSupplier.logException(AuthenticationResultSupplier.java:139)
at com.microsoft.aad.msal4j.AuthenticationResultSupplier.get(AuthenticationResultSupplier.java:88)
at com.microsoft.aad.msal4j.AuthenticationResultSupplier.get(AuthenticationResultSupplier.java:17)
at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1604)
at java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1596)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:175)

does anyone knows what could be the reason of getting this error?