Thanks Marc. It is working now.
I also simplified the script and replaced the variable to a hardcode text “Design now!” This is the modified script in case some else is looking for it:
/** Change "Choose Options" to "Design Now!" */?
function?my_custom_add_to_cart_text($text,?$product?=?null)?{?return?__(?'Design now!',?'woocommerce'?); }?add_filter('woocommerce_product_add_to_cart_text',?'my_custom_add_to_cart_text', 40);add_filter('woocommerce_product_single_add_to_cart_text',?'my_custom_add_to_cart_text');add_filter('woocommerce_product_variation_add_to_cart_text',?'my_custom_add_to_cart_text');