I checked on this for you and the content template screen is correct. Also your screenshot displays the correct output when you add a new content template.
It should open using the gutenburg editor. Is this not what you were expecting ? If you're not sure please let me know and I will clarify what is happening.
IT would appear that you want to edit the template using the classic editor.
My advise here is to rebuild the content template, however to do this you must first enable the classic editor by going to Toolset -> Settings -> Editing Experience and select "Show both the legacy and Blocks interface and let me choose which to use for each item I build".
From there under the content template option select Classic Editor.
Once you've done this please try creating a new content template to assign to the post type and let me know if the information starts Displaying on the frontend.
You mention that the issue was resolved on your test site when you tried the solution in the forum link correct?
Does the solution present any issues on the test site?
The problem is essentially being caused by theme compatibility as it would appear that we are unable to hook into the filter hook that is being used to display the content when trying to render the dynamically generated edit form.
Switching to a default wordpress theme on the copy of the site that I made works but your theme it doesn't
If the solution from the forum thread works with no issues then you can go ahead and implement it on your live environment.