MSGraph Mail Poller Plugin

Hello - We are trying to configure the MSgraph Mail Poller Plugin . The required values in the credential store are tenant , Client Secret and Application Id . We have given all the values but we are getting an exception as below :-

2021-08-09 19:28:56,733 [Appian Work Item - 1020 - execution02 : UnattendedJavaActivityRequest] DEBUG com.appiancorp.ps.msgraphmail.MSGraphMailPollerSmartService - Connecting to MS Graph authentication provider
2021-08-09 19:28:56,743 [Appian Work Item - 1020 - execution02 : UnattendedJavaActivityRequest] ERROR com.appiancorp.ps.msgraphmail.MSGraphMailPollerSmartService - 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)

Has anyone faced this issue ? 

What value are we suppose to use in Tenant field . The documentation says tenant endpoint which looks  usually something like https://login.microsoftonline.com/.onmicrosoft.com/ . we have passed it the value as 

https://login.microsoftonline.com/<our tenant domain>/ . Is this correct way ? 

Also , does this plugin use Oauth 2.0 ?  How is this getting the token to call MS graph API ?

Thanks 

Harveen