Do NOT use URL equals when creating a Custom conversions let you create rules for events or URLs so that you can better track and optimize for specific actions with Facebook ads. More or standard event with a URL rule.
Meta actually calls this out within their best practices document. When you use URL equals, no variations of that URL will be counted.
Why does that matter? Well, will “www” always appear or sometimes appear? Do you use UTM parameters or might UTM parameters automatically be injected? These variations won’t be counted.
Use URL contains instead. Just make sure that you use this in a way that isolates the URL you need.