The button should be visible to all users. I see that your buttons colours are set to white, therefore 'Publish' and 'Cancel' buttons are not visible.
Please read here how to change the colours, refer to Step 5: Customize the design of your buttons and backgrounds.
Let me know if it works!
Thank you to reply, that works if I go from Edit Site - Blog - Preview - Edit Post
But if I go from My Blog - Manage Posts - Dashboard - Edit Post, still white color I can't change.
Thank you Simona for the help!
now your case is more concrete - actually it is a bug and we are working on it. If in Dashboard you hover on the place where the buttons suppose to be, you'll see that the most indicator is changing and you actually can click the 'Publish' button, just it is not visible.
In the meantime you can create post from your live site, please read here more how it works.