Custom Login Not Working

I set up my custom login URL and checked “my site is behind a reverse proxy” as I use Cloudflare

Then I went to Cloudflare and entered my login URL for a page rule and set cache level to bypass and disable performance.

However, when I try to log in, it gives me the following error:

ERROR: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress.

I know my cookies are enabled because I will disable Cerber and everything will work fine again.

What am I doing wrong?