Here I am making another post to my blog, Roy.
It seems that when I sign in with my Google credentials, I see a "+ New Post" button on the "dashboard". Yet when I sign in exactly the same way as that only using your credentials, I don't see that. What I see instead is (I think) the "outsider's view" of the dashboard.
SO my conclusion would be that your blog is now "owned" by your Google credentials.
I don't have any more time to look at this now and/but maybe you can help by rethinking exactly how you created the blog.