Here's the module initialized by my Apache 1.3.x httpd.conf file:
LoadModule php4_module modules/mod_php4-4.1.2-module-mysql-mcrypt-ftp-imap.so
Here's my php config string from httpd.conf:
AddType application/x-httpd-php .php .php3 .php4 .phtml .html .htm
After the server is restarted, .html files which include php code are parsed correctly.
I know the string you referenced looks the same, so check for the proper module and be sure your server app supports php in this way. And make sure (as I know you must have!) to restart your server after saving the config changes.
Read your config string from the last character to the first, rather than the usual left-to-right. That way you can be more certain that there are no typographical errors. 🙂