here is the details error message:
Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=9.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: Exception retrieving custom activity info - Exception has been thrown by the target of an invocation.
Detail: <OrganizationServiceFault xmlns="schemas.microsoft.com/.../Contracts" xmlns:i="www.w3.org/.../XMLSchema-instance">
<ActivityId>77be9dbf-0c0c-41aa-a0ea-1f0cbfc886a5</ActivityId>
<ErrorCode>-2147200995</ErrorCode>
<ErrorDetails xmlns:a="schemas.datacontract.org/.../System.Collections.Generic" />
<HelpLink i:nil="true" />
<Message>Exception retrieving custom activity info - Exception has been thrown by the target of an invocation.</Message>
<Timestamp>2020-09-23T19:27:06.1668068Z</Timestamp>
<ExceptionRetriable>false</ExceptionRetriable>
<ExceptionSource i:nil="true" />
<InnerFault>
<ActivityId>77be9dbf-0c0c-41aa-a0ea-1f0cbfc886a5</ActivityId>
<ErrorCode>-2147200995</ErrorCode>
<ErrorDetails xmlns:a="schemas.datacontract.org/.../System.Collections.Generic" />
<HelpLink i:nil="true" />
<Message>Exception retrieving custom activity info - Exception has been thrown by the target of an invocation.</Message>
<Timestamp>2020-09-23T19:27:06.1668068Z</Timestamp>
<ExceptionRetriable>false</ExceptionRetriable>
<ExceptionSource i:nil="true" />
<InnerFault i:nil="true" />
<OriginalException i:nil="true" />
<TraceText i:nil="true" />
</InnerFault>
<OriginalException i:nil="true" />
<TraceText i:nil="true" />
</OrganizationServiceFault>
Server stack trace:
at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
Exception rethrown at [0]:
at Microsoft.Crm.Tools.Libraries.RegistrationHelper.RegisterPlugin(CrmOrganization org, CrmPlugin plugin)
at Microsoft.Crm.Tools.AssemblyRegistration.PluginRegistrationViewModel.btnregisterClick()