Hello,
This error might be related to the authentication method used and missing SPN definition.
This may help: Service Principal Name (SPN) configuration for Kerberos authentication (blueprism.com)
When using WCF connection mode without SPN defined, a Windows login screen may pop up. This has always be cancelled otherwise Windows may store this credentials and will fail every time without showing the login pop up again. In this case the stored credentials have to be removed manually as described here: Accessing Credential Manager - Microsoft Support
You have to look for entries for your servers and remove those only
You can also try to change the connection mode to .Net Remoting: Secure (it might be a good idea to disable callback port as having it enabled caused whole BP instanced becoming unresponsive). The BP SPN guide linked above says .Net Remoting: Secure also needs SPN defined but we didn't and it still works while WCF doesn't. (at least in BP 6.9, not sure if this is still the case for 7.3)
