You have an operation which creates a Confluence page with some content including Elements Connect fields display value (see Confluence mappings and Page Velocity variables). When you execute the operation, the page is created but the Elements Connect fields display value are not injected (left empty)
You are maybe trying to insert a display value which is an invalid HTML. Confluence tries to parse it and cannot retrieve a valid content so leaves it empty instead.
Check your Display template field configuration from the Elements Connect administration and make sure it generates a valid HTML.