WHMCS won't work with cloudflare, login just refreshes the page

I’ve installed WHMCS but the admin page login does not work with Cloudflare.

I’ve asked my host, 20i, and they point out it does work if we bypass the CDN by modifying a hosts files.

What happens is, you fill in the login credentials, press return, and the page just goes back to where it is, as if nothing happened.

I have page rules to bypass the director but it makes no differnce.

I have exhausted all other solutions.

Any ideas?

Managed to fix this by removing all proxies.