No such file error?

Tried logging onto my site recently and discovered this error message instead. I’ve tried re-loading the plugin via ftp, but there is no change. Ideas? Thanks, David

Warning: include_once(/data/25/2/129/25/2618677/user/2872693/htdocs/wordpress/wp-content/plugins/smooth-scroll-up//lib/ScrollupHandler.php) [function.include-once]: failed to open stream: No such file or directory in /data/25/2/129/25/2618677/user/2872693/htdocs/wordpress/wp-content/plugins/smooth-scroll-up/plugin.php on line 31

Warning: include_once() [function.include]: Failed opening '/data/25/2/129/25/2618677/user/2872693/htdocs/wordpress/wp-content/plugins/smooth-scroll-up//lib/ScrollupHandler.php' for inclusion (include_path='.:/usr/share/php:/usr/services/vux/lib/php') in /data/25/2/129/25/2618677/user/2872693/htdocs/wordpress/wp-content/plugins/smooth-scroll-up/plugin.php on line 31

Fatal error: Class 'ScrollUpHandler' not found in /data/25/2/129/25/2618677/user/2872693/htdocs/wordpress/wp-content/plugins/smooth-scroll-up/plugin.php on line 32

https://www.ads-software.com/plugins/smooth-scroll-up/