. . . . the Placeholder for the HTML Code (head) is adding the code, but the HTML Code (body) is not. . . . .
Assuming the HTML code has none of the following:
is enclosed in quotes
there are no typos
no extra ' or " in the code - if you use these they must always be in pairs
any procedural names variables etc are unique and do not replicate any of the Web Designer names
contains features such as PHP/MySQL which your host does not support
When you export or publish the web page including the code do you see the inserted body code in the HTML of the page where it has been added?
If you are not doing so I would recommend you export the website to a folder on the computer first and check the the site works correctly on your PC. Personally I check with several browsers Opera, Firefox, Chrome, and Edge before uploading.