Apologize for the inconveniences caused to you with this issue. We have included the wrong hooks.php file into the new release. This has been fixed and the download with the correct hooks.php file has been replaced.
Download a fresh copy of the v2.9.1 release and re-upload.
2018! A new challenge with a lot of changes coming up ...
We just released for all v3 and v4 Modules updates to be in compliance with the new upcoming WHMCS 7.5 system requirements for PHP 7.1. All modules have been reviewed and updated where necessary to work with PHP 7.1 and also to address some bugfixes.