There are many reasons a site might not load, such as misconfiguration, corrupt files, problems with a database, or something as simple as needing to clear your browser's cache and cookies on your computer.
Problems with the DNS
Make sure that you have the nameservers and DNS set correctly and it's had time to propagate. If you can access your site with its IP but not by typing in the domain name, it probably just needs more time to propagate. You can check the status of propagation by using whatsmydns.net. Please be aware that propagation may take up to 48 hours to complete. You can also flush your DNS cache on your computer to troubleshoot common connection issues between your computer and your website.
Your browser's cache could have another version of the site stored, causing the current version not to load. Try clearing your cache and your cookies and see if it solves the problem.
Disable any plugins, extensions, or custom themes that you have installed in the browser and see if that solves the problem. Some of them may be affecting how or if certain sites will load.