Thanks for your reply.
Don't worry, you're not sounding condescending - those are obvious questions.
1) & 2) the statements are in the .htaccess file in the top level of that software's directory.
3) RewriteRule /sub/dir/path/leading/to/page.html$ /sub/dir/path/leading/to/page.html.php [L]
Both files are in the same directory about 4 levels below root of that software. In the example above, consider the '/sub' part to represent the 1st level below the top level of that software's directory.
I tried that statement with and without the leading '/' since when the software is loaded, if it doesn't contain the slash after the directory name, it is automatically added.
4) I used the 'redirect' terminology for descriptive-purposes only. There was no error; no nothing. It's like it didn't find the original file in the first place so the RewriteRule appeared to be ignored.
Thanks again for your assistance.