Why I can not use ssl full(strip)model

Like I said, this is beyond what this community is made for. As Cloudflare does work properly and the error clearly points to your server, you will need to fix that on your server, but this is not related to Cloudflare.

Also, unblocking the port 443 is not enough, you need to serve requests through this port with your web server.

Please find a general IT support forum (Stackoverflow etc etc) which are handling general IT problems and how to make a web server serve under port 443 (encrypted traffic). But as there are just too many variables that will influence this, this forum is the wrong place to search for help, on how to set up your origin properly.

If you find any error that is related to Cloudflare, feel free to open a new thread. General advice: please make sure, your site work properly BEFORE adding it to Cloudflare - alternatively you can unproxy :grey: the respective DNS entries and make it work properly with HTTPS, then proxy :orange: it again and set the SSL mode to “Full (Strict)”.