Hi! I will try my best to help you. I have also faced similar problems learning. Have you configured the permissions on the steemconnect website correctly? What url are you using to login to steemconnect? Check if it has the comment authority on the scope "scope=vote,comment"
I think it is a scope issue, you can read more about scope at:
https://github.com/steemscript/steemconnect/wiki/OAuth-2
RE: (Part 4)Tutorial On SteemConnect JS Submit A New Post Using @steemconnect pt4