Cannot add Editor task in 3.5.1 .

Hello,

 

Lately, I'm trying to add an Editor task in GE 3.5.1 to a site, but it got an error message such as

 

Unable to cast COM object of type 'System.__ComObject' to interface type 'ESRI.ArcGIS.Carto.IMapServerObjects2'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{732DA8B0-BEB9-49B6-BF83-C1DF94F22AA0}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

 

Does anyone know what is going on?  We have Editor task in many sites before and still working, except this is a new site and it's not working.  Feel very strange ..

 

Thanks in advanced.

 

-Jennie