Hi, just purchased and installed event planner on a new wordpress environment and getting the below error, please can you assist

Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function “addTestimonialHook” not found or invalid function name in /homepages/32/d4296797654/htdocs/wordpress/wp-includes/class-wp-hook.php:309 Stack trace: #0 /homepages/32/d4296797654/htdocs/wordpress/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters(NULL, Array) #1 /homepages/32/d4296797654/htdocs/wordpress/wp-includes/plugin.php(476): WP_Hook->do_action(Array) #2 /homepages/32/d4296797654/htdocs/wordpress/wp-admin/includes/meta-boxes.php(1599): do_action(‘add_meta_boxes’, ‘page’, Object(WP_Post)) #3 /homepages/32/d4296797654/htdocs/wordpress/wp-admin/edit-form-blocks.php(274): register_and_do_post_meta_boxes(Object(WP_Post)) #4 /homepages/32/d4296797654/htdocs/wordpress/wp-admin/post-new.php(72): require(‘/homepages/32/d…’) #5 {main} thrown in /homepages/32/d4296797654/htdocs/wordpress/wp-includes/class-wp-hook.php on line 309
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