I need help with Blogger...

Why would I not be allowed to post comments on my own blog.

I have been trying to reply to other people's comments when they post about an entry of mine. Why would I not be able to post a reply comment to them? It always asks me to select a profile and when I select Google Account it always redirects me to the Google sign in page. I re sign in but still nothing. It takes me to a "preview" of my post I hit sumbit it redirects me to the Google sign in page. I need help. Any suggestions?