I hope this message finds you well. I am writing in response to the issue you raised regarding the Heading 1 not showing up on the Table of Contents (TOC).
Upon conducting a thorough investigation, we have discovered that the Heading 1 you mentioned is actually the title. As you can see in this screenshot: https://prnt.sc/wGXiXb1h3OCd, the title is not able to display on the TOC. However, if you place it in the post section, it will appear in the post, as shown in this screenshot: https://prnt.sc/iAvHAG48UyXG.
At our company, we value each and every one of our customers and always strive to provide the best possible service. We would like to assure you that we are here to help.
Please let us know if you have any further questions or concerns. We look forward to hearing from you.