try this:

EXEC sp_xml_preparedocument @idoc OUTPUT, @doc

SELECT * FROM OPENXML (@idoc, '/EVENT_INSTANCE',1)

I'm glad that my 1 year old post was able to help. Happy coding to all 😉

I experienced same problem and manage to fix it by adding the field AwaitingFirstExecution with bit datatype in table SessionData in ReportServerTempDB database

Hope it helps...