Hi @Gigcoyle,
Actually, you simply need to go to WordPress Dashboard > Reading and set the page in question as your main blog page.

Then you can go to Pro > Headers and add a new header and set that header to the page in question with no problem.
kindly get back to us with the result of the steps above and URL/User/Pass of your WordPress dashboard using the Secure Note functionality of the post to follow up the case if you still have problems.
Thank you.