NOT INSTALLING

Plugin could not be activated because it triggered a fatal error.

Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function "activate_wos" not found or invalid function name in /home/jouleswitches/public_html/wp-includes/class-wp-hook.php:307 Stack trace: #0 /home/jouleswitches/public_html/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters('', Array) #1 /home/jouleswitches/public_html/wp-includes/plugin.php(476): WP_Hook->do_action(Array) #2 /home/jouleswitches/public_html/wp-admin/plugins.php(194): do_action('activate_orders...') #3 {main} thrown in /home/jouleswitches/public_html/wp-includes/class-wp-hook.php on line 307