Unable to refresh - show object reference not set to an instance of an object.

[questions]

I am not able to refresh my power BI at desktop and get below message. Can you help?

Feedback Type:
Frown (Error)

Timestamp:
2020-09-23T04:29:09.9309179Z

Local Time:
2020-09-23T12:29:09.9309179+08:00

Session ID:
ca5c3cb5-f882-4035-b084-4a8fb5628653

Release:
August 2020

Product Version:
2.84.701.0 (20.08) (x64)

Stack Trace:
at Microsoft.Mashup.Evaluator.ChannelMessenger.CreateChannel()
at Microsoft.PowerBI.Client.OleDbProvider.PowerBIMashupDataSource.EvaluationSession.Dispose()
at Microsoft.Mashup.Host.ProviderShared.PackageMashupEvaluator.<>c__DisplayClass7_0.<Evaluate>b__1(Object o)
at Microsoft.Mashup.Evaluator.Interface.InvokeManyAction`1.CheckDone()
at Microsoft.Mashup.OleDbProvider.DataHost.MashupEvaluator.<>c__DisplayClass4_1.<Evaluate>b__1()
at Microsoft.Mashup.OleDbProvider.DataHost.AsyncResultIDataReaderSourceHelper.InvokeThenOnDispose(Action`1 callback, AsyncResult`1 result, Action action)
at Microsoft.Mashup.OleDbProvider.DataHost.MashupEvaluator.<>c__DisplayClass4_0.<Evaluate>b__0(EvaluationResult2`1 result)
at Microsoft.Mashup.Evaluator.Interface.EvaluationResultExtensions.InvokeThenOnDispose(Action`1 callback, EvaluationResult2`1 result, Action action)
at Microsoft.Mashup.Evaluator.Interface.EvaluationResultExtensions.InvokeThenOnDispose[T](Action`1 callback, EvaluationResult2`1 result, Action action)
at Microsoft.Mashup.Evaluator.LimitedDocumentEvaluatorFactory.Evaluation`1.Complete(EvaluationResult2`1 result)
at Microsoft.Mashup.Evaluator.Interface.EvaluationResultExtensions.InvokeThenOnDispose(Action`1 callback, EvaluationResult2`1 result, Action action)
at Microsoft.Mashup.Evaluator.Interface.EvaluationResultExtensions.InvokeThenOnDispose[T](Action`1 callback, EvaluationResult2`1 result, Action action)
at Microsoft.Mashup.Evaluator.DocumentEvaluator.<>c__DisplayClass7_0`1.<BeginGetResult>b__0(EvaluationResult2`1 result)
at Microsoft.Mashup.Evaluator.Interface.EvaluationResultExtensions.InvokeThenOnDispose(Action`1 callback, EvaluationResult2`1 result, Action action)
at Microsoft.Mashup.Evaluator.Interface.EvaluationResultExtensions.InvokeThenOnDispose[T](Action`1 callback, EvaluationResult2`1 result, Action action)
at Microsoft.Mashup.Evaluator.LimitedDocumentEvaluatorFactory.Evaluation`1.Complete(EvaluationResult2`1 result)
at Microsoft.Mashup.Evaluator.RemoteDocumentEvaluator.RemoteEvaluation`1.TryComplete(EvaluationResult2`1 result)
at Microsoft.Mashup.Evaluator.RemoteDocumentEvaluator.RemoteEvaluation`1.TryCompleteWithException(Exception exception)
at Microsoft.Mashup.Evaluator.RemoteDocumentEvaluator.RemoteEvaluation.Evaluate(Boolean enableFirewall)
at Microsoft.Mashup.Evaluator.EvaluatorThreadPool.EvaluatorThread(Object state)
at Microsoft.Mashup.Evaluator.SafeThread2.<>c__DisplayClass9_0.<CreateAction>b__0(Object o)

PowerBINonFatalError:
{"AppName":"PBIDesktop","AppVersion":"2.84.701.0","ModuleName":"","Component":"Microsoft.Mashup.Evaluator.ChannelMessenger","Error":"Microsoft.Mashup.Host.Document.SerializedException - System.NullReferenceException","MethodDef":"CreateChannel","ErrorOffset":""}

OS Version:
Microsoft Windows NT 10.0.17134.0 (x64 en-US)

CLR Version:
4.7 or later [Release Number = 461808]

Peak Virtual Memory:
38.6 GB

Private Memory:
647 MB

Peak Working Set:
935 MB

IE Version:
11.1667.17134.0

User ID:
afd765c8-c28a-4682-84fe-7a51a434a187

Workbook Package Info:
1* - en-US, Query Groups: 4, fastCombine: Disabled, runBackgroundAnalysis: True.

Telemetry Enabled:
True

Snapshot Trace Logs:
C:\Users\amchan\AppData\Local\Microsoft\Power BI Desktop\FrownSnapShot829766040.zip

Model Default Mode:
Import

Model Version:
PowerBI_V1

Is Report V3 Models Enabled:
False

Enabled Preview Features:
PBI_NewWebTableInference

Disabled Preview Features:
PBI_shapeMapVisualEnabled
PBI_SpanishLinguisticsEnabled
PBI_ImportTextByExample
PBI_qnaLiveConnect
PBI_inlineExplore
PBI_v3ModelsPreview
PBI_dataSearchCuration
PBI_azureMapVisual
PBI_dataPointLassoSelect

Disabled DirectQuery Options:
TreatHanaAsRelationalSource

Cloud:
GlobalCloud

DPI Scale:
100%

Supported Services:
Power BI

[v-chuncz-msft]

@questions 

I cannot reproduce the issue. You may try the latest version and create a support ticket for assistance if necessary.