In my case, seems that the original file '/usr/local/apache/conf.d/vhosts.conf' was emptied.
My customer (the root admin in a VPS server) has been deleted a site, and I find that file was empty.
In an another server, I have that file with the original configuration, with the following content:
==========================================
IncludeOptional /usr/local/apache/conf.d/vhosts/*.conf
==========================================
So, instead to configure as my earlier post, change like this.
The server is working now.
For now, all that remains is to know why this happened to that file.
May be a bug..??