Cloudflare has posted an updated list of IPv4 addresses. If you’re using Fail2WP and Cloudflare, you should update the Fail2WP configuration for Cloudflare IPv4 addresses to this list:
103.21.244.0/22
103.22.200.0/22
103.31.4.0/22
104.16.0.0/13
104.24.0.0/14
108.162.192.0/18
131.0.72.0/22
141.101.64.0/18
162.158.0.0/15
172.64.0.0/13
173.245.48.0/20
188.114.96.0/20
190.93.240.0/20
197.234.240.0/22
198.41.128.0/17
You can find all Cloudflare IPv4 and IPv6 addresses here: www.cloudflare.com/ips/