FixRunner.com explains how you can solve the problem of a 404 Error when logging into WordPress.
What’s the problem?
You try to log into your WordPress admin panel but you receive a 404 Error page.
How to fix a 404 Error when logging into WordPress
When you receive a 404 Error Login in WordPress, it is a sign that you may need to update your URL in the database. Follow the next steps if you are able to access phpMyAdmin:
If you are not able to access phpMyAdmin, try the following steps instead to update your folder attributes: