403 error - Cannot serve directory : No matching DirectoryIndex

Symptoms

After creating an account or addon domain, you encounter a 403 error on the new domain's site. The Apache error log also shows an error similar to the following.

[Mon May 17 02:12:02.952827 2021] [autoindex:error] [pid 8506:tid 47719184406272]
[client 111.222.33.44:49999] AH01276: Cannot serve directory 
/home/username/public_html/: No matching DirectoryIndex (index.php,index.php8
,index.php7,index.php5,index.perl,index.pl,index.plx,index.ppl,index.cgi,index.jsp,
index.jp,index.phtml,index.shtml,index.xhtml,index.html,index.htm,index.js) found,
and server-generated directory index forbidden by Options directive

Description

The issue occurs when the site's DirectoryIndex value is set to a file that doesn't exist in the site's document root, and the Indexes option is disabled.

Workaround

Ensure the site's index (home) page is in the site's document root and its filename is on the DirectoryIndex line of the site's .htaccess file.

Additional resources

DirectoryIndex Priority