java.util.concurrent.ExecutionException: java.lang.Exception: Server returned error in RSTR - ErrorCode: FailedAuthentication : FaultMessage: Authentication Failure

Question

We have created an Azure app and granted all required permissions for two different email ids but with one we are able to acquire the token and with the other we are getting below error. The email IDs have no any 3rd party authentication like Okta.

Why is the same app working for an email and not working for the other one?

// Code snippet
UserNamePasswordParameters parameters = getUserNamePasswordParameters(scopes, username, password);
Future<IAuthenticationResult> aResult = app.acquireToken(parameters);
IAuthenticationResult result = (IAuthenticationResult)aResult.get();

2021-08-24 14:03:41,785 ERROR [Thread-200] [com.microsoft.aad.msal4j.PublicClientApplication] [] [dd.trace_id= dd.span_id=] [Correlation ID: REMOVED] Execution of class com.microsoft.aad.msal4j.AcquireTokenByAuthorizationGrantSupplier failed.: java.lang.Exception: Server returned error in RSTR - ErrorCode: FailedAuthentication : FaultMessage: Authentication Failure
at com.microsoft.aad.msal4j.WSTrustResponse.parse(WSTrustResponse.java:88)
at com.microsoft.aad.msal4j.WSTrustRequest.execute(WSTrustRequest.java:48)
at com.microsoft.aad.msal4j.WSTrustRequest.execute(WSTrustRequest.java:70)
at com.microsoft.aad.msal4j.AcquireTokenByAuthorizationGrantSupplier.processPasswordGrant(AcquireTokenByAuthorizationGrantSupplier.java:76)
at com.microsoft.aad.msal4j.AcquireTokenByAuthorizationGrantSupplier.execute(AcquireTokenByAuthorizationGrantSupplier.java:33)
at com.microsoft.aad.msal4j.AuthenticationResultSupplier.get(AuthenticationResultSupplier.java:59)
at com.microsoft.aad.msal4j.AuthenticationResultSupplier.get(AuthenticationResultSupplier.java:17)
at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1604)
at java.lang.Thread.run(Thread.java:748)