What is the domain name?
Hopefully you have the SSL certificate at your host/origin.
Do you have port 80 and 443 open at your host/origin?
Port 80 and 443 are both compatible as others as follows on the article below:
https://support.cloudflare.com/hc/en-us/articles/200169156-Identifying-network-ports-compatible-with-Cloudflare-s-proxy
I see you use Nginx and proxy your app over port 5000.
Have you allowed the Cloudflare IP addresses to connect to your host/origin?
A good way to check with the steps as written below:
https://support.cloudflare.com/hc/en-us/articles/115003011431-Troubleshooting-Cloudflare-5XX-errors#522error