Order of leviathan

Message for Siteground . We are having issues logging into one of my clients WordPress sites which is parked under a domain in Cpanel. All the pages are viewable or Chrome and Firefox browsers. Our problem is being able to login inside the WordPress dashboard. Can you fix this.?

we cannot login using wp-admin or wp-login.php

History of how we built the site in the beginning:

I built the new site using a subdomain in our of our Cpanel accounts..https://orderofleviathan.mutinymagazine.net/

Then I had the site migrated to the new domain orderofleviathan.com using the Siteground Migrator tool. I followed the steps correctly and now we still cannot log inside the WordPress dashboard. I keep getting too many redirect errors. PLEASE FIX THIS PROBLEM.