I am being tasked with running multiple WordPress instances, and I decided to work it on the same server. When running into issues doing things like this, have a procedure for checking into issues. For example, check your configurations. If they align, then look into other places where they diverge, for example DNS records. Work your way through each section confirming all information is correct, because you will likely find that a typo or other small error occurred that wouldn’t trigger any alarms or failures, but will totally gunk up the operation.