
I don't know what's happened. Yesterday its was working fine, but I did some changes that can be the cause of the problem. I will say what I did.
We installed the plugin Spam be gone, and Custom pages but we didn't configure it. We also configure Cloudflare and activate the options to reduce the size for css, javascript and html. We also activate the option to transform HTTP to HTTPS in CF. Later I disable the option to login to the server using ssh with password, so we can only login with our ssh keys. I dont know if the login was blank yesterday after all those changes, but today is blank.
Today we deactivate and remove the plugins and Cloudflare, rebuild and start the server again, but the problem remains. I still have the option to only login with ssh keys in the server.