Still cannot access control panel

Whilst HTTPS is working fine, I cannot access the site’s control panel.

Adding the following modified to reflect the domain name doesn’t work.

define( 'WP_SITEURL', 'https://example.com');

define( 'WP_HOME', 'https://example.com');

nor does flushing/disabling/bypassing Cloudflare make any difference.

Also running GTmetrix on the URL for the control panel eventually times out and returns

“Redirect loop detected!

Visiting the page has resulted in an endless chain of redirects. This is usually caused by a problem in your application.“

Any ideas will be greatly welcome, for I have decided to migrate to another hosting company and I am stuck! Help!

The page I need help with: [log in to see the link]