A browser follows only a limited number of redirects before it gives up. The message ERR_TOO_MANY_REDIRECTS therefore means address A sends you to B and B sends you back to A. The site is not broken, but two rules disagree about which address is the right one.
A loop tied to logging in can keep spinning because of cookies alone, even when the server is already fine. Delete the site cookies or open the address in a private window. If the site works there, the fix is already in place and your browser simply remembered the old state.
WordPress has two addresses, the site address and the WordPress address. If one says https://example.com and the other https://www.example.com, they redirect to each other forever. Both must be in exactly the same form, same scheme and same www choice.
If you cannot reach the admin, the values can be set temporarily in wp-config.php with define('WP_HOME','https://example.com'); and define('WP_SITEURL','https://example.com');.
A common situation is the same rule applied twice, once in the server settings or the hosting panel and once by hand in .htaccess. Both do their job and the result is a circle. Keep one place that handles the https rule and one that handles the www choice.
If you run a plugin that forces https while the server already does the same, you get exactly this loop. On Nordweb hosting the certificate and the redirect are handled on the server, so a separate forcing plugin is not needed. Setting up the certificate is covered in our guide to taking an SSL certificate into use.
If the domain runs through a proxy or a CDN, it may talk to the server unencrypted while the server insists on an encrypted connection. The server redirects to https, the proxy comes back unencrypted, and the circle is complete. The name of the setting varies by service, but the right choice is always the one that delivers the traffic encrypted all the way.
Then it is a single redirect rule pointing at itself. This happens easily when an old address is redirected to a new one and the new one contains a typo. Setting up redirects correctly is covered in our guide on pointing a domain to another address, and broken addresses in our guide on fixing a 404 error.
Do not add a new redirect to fix the old one. The loop gets longer but it does not break. Take a copy of .htaccess before editing so you can return to the starting point in a second.
We find which of the two rules is the extra one and remove it, so the site opens on one address without the detour. We also make sure search engines see one address rather than two.
