You’re probably using SSL in Strict mode, and there’s no SSL certificate on your server. Your server needs an SSL certificate for your domain to be able to use Strict mode.
Showing ns40.domaincontrol.com and ns39.domaincontrol.com and not the Cloudflare name servers.
It also shows the domain is just parked domain
When/if you resolve that then set the A record to the 50.xx.xx.xx IP (if that the proper IP to your host.
One thing to remember with DNS you can’t switch nameservers back and forth. You must set them and wait for full propagation (some times several hours).,When testing your site, make sure you are using DevTools and not caching or manually clearing cache (not refresh) each time you check.