There’s most likely some rule in one of your apache configuration files (or .htaccess) denying access to dot files or directories. Some people consider this best-practice to prevent accidentally leaking things like .git or .svn directories which contain all your source code.
This could be done in any number of ways. Look out for something like:
<FilesMatch "^\.">
or
<DirectoryMatch "^\.|\/\.">
or
RewriteRule (^\.|/\.) - [F]
There’s probably plenty of other ways this could be done.