Not able to connect to website

May I ask who is your hosting provider?

Have you tried following the steps from as written in the article from below?:

https://support.cloudflare.com/hc/en-us/articles/115003011431-Troubleshooting-Cloudflare-5XX-errors#522error

Have you allowed Cloudflare IP addresses to connect to your new host/origin?
Maybe you need to check and allow Cloudflare IP addresses to connect to your host/origin server:
https://support.cloudflare.com/hc/en-us/articles/201897700-Allowing-Cloudflare-IP-addresses

Have you got an SSL certificate for the needed hostnames of the domains?
Can you check what have you got selected under SSL tab at Cloudflare dashboard? Is it Full SSL or Flexible SSL or something other?