Custom unsubscribe page will not loaded

I’m having the same issue. This is the first time I’ve tried to implement it, I’ve followed almost every guide and I’m pretty sure that I’m not missing anything yet I cannot get this custom unsubscribe page to work. I also think this isn’t a very common feature people use so that’s why I don’t see a lot of people complaining about it. However, this seems to be a pretty old issue, see the following posts: