Hello Victor,
If multiple authentication methods are enabled on the remote Host (e.g. Single password, AND RU Security etc.) the program still uses one of them during a connection. Which one depends on your settings on the Viewer side -> Connection properties -> Authentication tab.
If
Auto is set the Viewer uses the first available authentication method according to this order:
Custom Server Security (CSS)
Windows Security
Remote Utilities Security
Single password
As you can see, since you have enabled RU Security and Single password and have your auth method set to Auto, Viewer will always force RU Security when you authenticate.
To override this behavior for specific Hosts you just need to select the desired authentication method in the drop down list and Viewer will always use that. In your example just select Single password to override the automatic sequence check.
Hope that helps.