I need a page or menu on my website to be fixed

My wordpress 5.7.6 website https/www.gastrolondon.co.uk has a page on acid reflux. For some reason, when you click to see this page: https/www.gastrolondon.co.uk/acid-reflux/ it sends me to the blog post called https/www.gastrolondon.co.uk/acid-reflux-2/. I renamed the blog post to acid reflux blog and also unpublished it but I simply cannot get the system to recognise the original page of acid-reflux.
I need somebody to sort this out so that when people click on the menu the page reappears correctly. I suspect it is a very simple job for somebody who understands WordPress well. I have developed the website myself so I know a fair amount but I simply can't work out what the problem is.