So i use Cloudflare and when i turn the ssl to flexible everything works fine but when i go to full it just loads the known error page by Cloudflare and says cant connect to host and on the screen its Error 521, so my question is how do i fix it, i think it might have a problem with my domain maybe? because its a .dev domain and i noticed on certbot that it only connected with a certificate and it wasnt possible to enter the domain through http so maybe thats a problem but how do i fix it?
Before moving to Cloudflare, was your Website working over HTTPS connection?
Can you double-check if your web hosting provider issued an SSL certificate which is still a valid one for your domain(s)? 
Before doing anything at Cloudflare settings, you could determine if you have a valid SSL certificate installed at the origin host/server by your web hosting provider or your own VPS/dedicated server following the steps from below:
- Use the “Pause Cloudflare on Site” option from the Overview tab for your domain at dash.cloudflare.com .
- The link is in the lower right corner of that page.
- Give it five minutes to take effect.
- Check with your hosting provider / cPanel AutoSSL / ACME.sh / Certbot / Let’s Encrypt or some other and renew it accordingly.
- Make sure site is working as expected without any errors via HTTPS.
- Only then should you un-pause Cloudflare and double-check your SSL/TLS setting to make sure it’s Full (Strict).
Here is a way to re-check if you correctly setup the SSL for your domain with Cloudflare:
1 Like
Thank you very much! I changed to Cloudflare because i wanted and SSL because Certbot blocked my certificate requests because i did to much so then ill have to wait until i can generate a new one and activate my certificate and then i can just turn on Full strict when the SSL Certificate is on and everything works without any other settings?
This topic was automatically closed 3 days after the last reply. New replies are no longer allowed.