There is a save button in the page builder.
The content in a page-builder gets saved with the "save changes" button. Try adding the form and click the "save changes" instead of update.
p.s : Make sure the page is already published.
We checked your site ,it seems your database entry for the corresponding post "become and instructor" seems to have corrupted somehow .
Please delete the page " become and instructor " and create a new one .