Have you checked this under DNS in your Cloudflare dashboard?
The errors “The page isn’t redirecting properly” or “ERR_TOO_MANY_REDIRECTS” indicates a redirect loop between Cloudflare and your origin server. The easiest fix for this is to remove the redirect on your origin server. For a more detailed set of options, review the troubleshooting suggestions in this Community Tip.
Thanks for replying so far. When you say removing redirects on Origin Server, what do you mean? If we can Private Message, I can give you all the DNS details, unless prividing the URL here is acceptable?
If you already have SSL on the server and you redirect all requests from HTTP to HTTPS, when Cloudflare tries to access the server over HTTP, it gets a redirect to HTTPS. Because it is set to Flexible, it forces that back to HTTP and the server redirects it to HTTPS and so on… Hence the loop!
Full (strict) is much more secure and causes less issues - really everyone should be using it!