Links suddenly not working causing 404 errors

My application was working fine but today I discovered that all links to my listings are broken. The search function works fine to get all the listings but when you click to get a listings’ details you get a 404 error.
From the search result I use a link to external page with dynamic link to the listing ID. This is an example.

Has something changed recently to make this functionality not work?
Any help would be appreciated.

This sounds more like an application issue with the format of the URL - as it is every URL- but if it is that the third party links are no longer working, and you want to automatically test them in your application, I built this plugin to solve exactly this problem - Broken Link Checker.

If it isn’t quite what you are looking for let me know - it could be easy to adapt it to do what you want.