I am currently receiving the error message "Authorization Required! Your authorization with eBay has expired or is invalid. Please login with eBay to renew." but unfortunately there is nothing in your Help pages that explain how to do this. I have searched in eBay also, including Permissions in my Account Settings but there is nothing obvious there. What's the trick?

Hello Robert,
Thank you for your question. You can authorize by clicking on "Preferences." The "Log in with eBay" is at the top. It's also any "sign up" link, as they are the same thing -- the link is for both signing up and refreshing the auth.
We'll take steps to clarify this in the next release. Thank you for the feedback.