soap:ServerServer was unable to process request. ---> Cannot load event receiver assembly ‘Nintex.Hawkeye.SharePoint, Version 184.108.40.206, Culture=netural, PublicKeyToken=8e6c22a2b4511ea7.’
This error is due to records in the dbo.EventReceivers table for Hawkeye that contained a Null value for the SiteID.
1. Remove those records
2. Run NWAdmin.exe -o UpgradeDatabases
3. Publish a workflow.