This is the only code in the hook file. Can't imagine it's outdated. Nothing get's logged in the module log. I should add that I tried adding that hook to the "includes/hooks/example.php" file and it worked. I also have an addon module on the WHMCS installation, and it's hooks are working fine too. Seems to be just the provisioning module.
<?php
if (!defined("WHMCS"))
die("This file cannot be accessed directly");
add_hook('EmailTplMergeFields', 1, function ($params) {
return array(
'multicraft_server_id'=>'Multicraft Server ID',
);
logModuleCall('server module', 'testhook');
});