Cloudflare and ssl on apache2 521 Web server is down

I have webpage hosted on apache2 on Ubuntu and Cloudflare . I configured SSL on Apache and now I want to change to not use SSL from Cloudflare but from the Apache on Ubuntu. Configuration in '/etc/apache2/sites-available/my-web-ssl.conf`:

SSLCertificateFile     /etc/ssl/certs/myweb.crt
SSLCertificateKeyFile   /etc/ssl/certs/myweb_priv.key
SSLCertificateChainFile /etc/ssl/certs/ComodoRSACA.crt

Test apache2 configuration:

 sudo apachectl configtest
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message
Syntax OK

But when I change in Cloudflare SSL on full it doesn’t work:

ERROR 521

According to this list: Cloudflare tip fixing error 521

I added every port to allowed in ufw:

sudo ufw status
Status: active

To                         Action      From
--                         ------      ----
Apache                     ALLOW       Anywhere
443/tcp                    ALLOW       Anywhere
80/tcp                     ALLOW       Anywhere
22/tcp                     ALLOW       Anywhere
20,21,10000:10100/tcp      ALLOW       Anywhere
13/tcp                     ALLOW       Anywhere
14/tcp                     ALLOW       Anywhere
18/tcp                     ALLOW       Anywhere
15/tcp                     ALLOW       Anywhere
17/tcp                     ALLOW       Anywhere
29/tcp                     ALLOW       Anywhere
32/tcp                     ALLOW       Anywhere
Apache (v6)                ALLOW       Anywhere (v6)
443/tcp (v6)               ALLOW       Anywhere (v6)
80/tcp (v6)                ALLOW       Anywhere (v6)
22/tcp (v6)                ALLOW       Anywhere (v6)
20,21,10000:10100/tcp (v6) ALLOW       Anywhere (v6)
13/tcp (v6)                ALLOW       Anywhere (v6)
14/tcp (v6)                ALLOW       Anywhere (v6)
18/tcp (v6)                ALLOW       Anywhere (v6)
15/tcp (v6)                ALLOW       Anywhere (v6)
17/tcp (v6)                ALLOW       Anywhere (v6)
29/tcp (v6)                ALLOW       Anywhere (v6)
32/tcp (v6)                ALLOW       Anywhere (v6)

In httpd.conf I don’t have any modules listed in above list. But still have 521 error

What’s the URL giving the 521 error?

Also, here are troubleshooting steps for 5xx server errors