2 WordPress Instances, 1 server – How to switch instance

Mapping a domain, call it abc.uri.edu, to site #4 on wp.apps.uri.edu.
Copied the site to a new instance of WordPress on the same server.
Tried mapping abc.uri.edu to site #2 on wp.apps2.uri.edu.
Did not work, after deleting the mapping from site #4, when the url abc.uri.edu gets typed into a browser, what comes back is:
http://wp.apps.uri.edu/wp-signup.php?new=abc.uri.edu
and the content of the page is site #1 of wp.apps.uri.edu.
I suspect that there are some files that need to be deleted from the directories in wp.apps.uri.edu.
Any guesses?

https://ww.wp.xz.cn/plugins/wordpress-mu-domain-mapping/