Well for me its the same thing if i run one masternode or two.
When i had one this command gave me the same error.
Now i have two and its still "This is not a masternode (code -1)" message when i type "masternode status".
When i start them it says successful for both. I can see them working with masternode list, its just this command gives me that error.
Yeah, I'm getting the same error now as well. Not sure what the problem is there, was working before. I'll remove it from the guide for the time being.