If you are seeing a "Firefox has detected that the server is redirecting the request for this address in a way that will never complete" message, the problem may be resolved by removing cookies or history associated with the site, but you might also need to check the cookies exceptions list in Firefox; that's how I was finally able to resolve a problem accessing a particular site that I could access in another browser on a system, but not with Firefox.
When trying to log into the Rakuten Marketing website using Firefox 52.0.1 on a Windows 10 system, I saw the message below after being redirected to http://cli.linksynergy.com/cli/common/login.php:
The page isn't redirecting properly
Firefox has detected that the server is redirecting the request for this address in a way that will never complete.
• This problem can sometimes be caused by disabling or refusing to accept cookies.
[ More Info ]