One possible Root cause - you are logged in via your second account.
This is the same issue I had. The UI from the earlier google home tutorials have been changed a bit. So after clicking the actions on google in api.ai we are redirected to to actions on google page. (Previously it was sent to the web simulator straight)
I created a project called personal butler in api.ai but what I saw was a project called API project, so when I clicked it and try to simulate it I got the exact error.
I registered to api.ai from my secondary google email. So when I was redirected to the actions on google page, it logged in via the primary account. After I signed out and loged in via the same account I was able to see my project and it was working fine.
PS - When testing with google home also the same account should be used in the andriod app