The page you are trying to reach does not exist, or has been moved

I’ve added a new page to my administration panel that allows us to post aircraft that’s for sale. It allows me to submit the form, and it even registers as being sent to the database, seeing as tho it shows the post in the dash board. But if you try to visit the page, it says “The page you are trying to reach does not exist, or has been moved. Please use the menus or the search box to find what you are looking for. ” Here is the code I’ve added to the functions.php file in my child theme.

https://pastebin.com/1hexjwaT