Can't Activate "WooCommerce Checkout Manager Pro"

After uploading the plugin, I can’t activate “WooCommerce Checkout Manager Pro.”

At first I thought it clashed with “WooCommerce Checkout Manager” free version. Then I uninstalled it first.
But still I can upload “WooCommerce Checkout Manager Pro,” but can’t activate it.
Following message appears:

Plugin could not be activated because it triggered a fatal error.
Fatal error: Cannot redeclare wccs_install() (previously declared in /home/cleaflow/public_html/wp-content/plugins/woocommerce-checkout-manager/woocommerce-checkout-manager.php:29) in /home/cleaflow/public_html/wp-content/plugins/woocommerce-checkout-manager-pro/woocommerce-checkout-manager-pro.php on line 132

Please help promptly. Thanks.

https://wordpress.org/plugins/woocommerce-checkout-manager/