All websites are down with 502 Bad Gateway error: apache2 or httpd is not running

Symptoms

• All websites on the Plesk server are showing a 502 Bad Gateway error while opened in a browser

• Attempts to start Apache and Apache configuration tests fail with an error that is similar to the following:

  AH00526: Syntax error on line 51 of /etc/apache2/plesk.conf.d/vhosts/example.com.conf:
  SSLCertificateFile: file '/opt/psa/var/certificates/cert1Ape62' does not exist or is empty

• The following error is shown in the Plesk GUI:

  New configuration files for the Apache web server were not created due to the errors in configuration templates: nginx: [emerg] BIO_new_file("/usr/local/psa/var/certificates/cert1Ape62") failed (SSL: error:02001002:system library:fopen:No such file or directory:fopen('/usr/local/psa/var/certificates/cert1Ape62','r') error:2006D080:BIO routines:BIO_new_file:no such file) nginx: configuration file /etc/nginx/nginx.conf test failed . Detailed error descriptions were sent to you by email. Please resolve the issues and click here to generate broken configuration files once again or here to generate all configuration files. See the details in Configuration Troubleshooter

• That SSL certificate that is reported in the error message has zero size:

  • For RHEL-based OS (CentOS, CloudLinux, RedHat:

    # ls -l /usr/local/psa/var/certificates/cert1Ape62
    ...
    -r-------- 1 root root 0 Mar 24 12:26 /opt/psa/var/certificates/cert1Ape62

  • For Debian-based OS (Debian, Ubuntu):

    # ls -l /opt/psa/var/certificates/cert1Ape62
    ...
    -r-------- 1 root root 0 Mar 24 12:26 /opt/psa/var/certificates/cert1Ape62

• The Plesk web server reconfiguration utility fails with an error that is similar to the following:

  # /usr/local/psa/admin/bin/httpdmng --reconfigure-domain example.com
  ...
  ERR [panel] Apache config (14972022740.47990300) generation failed: Template_Exception: Syntax error on line 51 of /etc/httpd/conf/plesk.conf.d/ip_default/example.conf:
  SSLCACertificateFile: file '/usr/local/psa/var/certificates/cert1Ape62' does not exist or is empty

• Repairing files system permissions with the plesk repair utility results in an error that is similar to the following:

  # plesk repair fs -y -v
  Checking Linux system files ......................................... [OK]
  Checking virtual hosts' file system
  There are incorrect permissions on some items in the system
  directory for the domain 'example.com' .......................... [ERROR]
  - Failed to stat
  /var/www/vhosts/system/example.com/conf/webalizer.conf: No
  such file or directory
  Repairing incorrect permissions ................................. [FAILED]
  - openat 'webalizer.conf' failed: No such file or directory
  Failed to open safely
  /var/www/vhosts/system/example.com/conf/webalizer.conf: No
  such file or directory

• All websites on the server are not accessible, while showing a browser error that is similar to the following :

  ERR_CONNECTION_REFUSED

Cause

The SSL certificate file that is reported in the error message is missing or is corrupted, due to which it has an improper size or is not found at all.

Resolution

Note: If the domain example.com was removed previously from the server, apply the solution from the article: Apache or nginx fails to start: BIO_new_file: certificate not found: No such file or directory: nginx: configuration file /etc/nginx/nginx.conf test failed…