This is a Blogger problem, NOT Nablle.
Nabble doesn't set a height because, unless an author specifies otherwise, a page will expand to allow for the content it contains.
In your case, you have set a height on your blogger page that limits the height available for your Nabble application. (The "View More" link below the forum proves that!)
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.