Why my .htaccess is not working?

Hi,

I am trying to rewrite this URL:

https://maxmon.softnames.com/activat...4-0cc47a4422ec

to be like this:

https://maxmon.softnames.com/activat...4-0cc47a4422ec

but it's redirecting to home page which I assume it's 404 but the file is already there if I run it using the normal URL above

How can I fix this issue please?

Here is my .htaccess:

# Disable Directory Listings in this Directory and Subdirectories
# This will hide the files from the public unless they know direct URLs
Options All -Indexes

RewriteEngine On

ErrorDocument 404 https://maxmon.softnames.com/

RewriteCond %{HTTP_HOST} ^maxmon.softnames.com[nc]
RewriteRule ^activate/([^/]*)/([^/]*)/([^/]*)\.html$ /activate.php?activation_secret=$1&customer_guid=$2&activation_guid=$3 [L]


Thanks,
Jassim