Can you check your application logs?

Also, this doesn't look like the case but make sure the port the URL is mapped to is the same as the URL the application is listening to.

Nothing in the application logs, i dont think the request is even reaching it. Nothing in the project logs either.

Port is correct, the magic railway link works when enabled on the same port, its only with the custom domain that it doesnt.

DNS DNS DNS always DNS - internal DNS on my side was blocking it due to it being a brand new domain