Hello,
We have taken our website’s backup from two months back and checked whether our issue is resolved or not.
We found that the website designing issue is resolved but the issue we were having for the single product page builder and header builder isn’t resolved yet.
It’s some error or bug from your end only. Please check it we have tried editing previous templates and created new ones as well but still, it’s giving us the same error of POST NOT FOUND! we are not able to edit anything.