Please add the given code in your wplms-customizer.php file in wplms customizer :
add_filter('wplms_course_thumb_extras','add_add_to_cart_link_course_block');
function add_add_to_cart_link_course_block($html){
global $post;
$product=get_post_meta($post->ID,'vibe_product',true);
if( !empty($product) && is_array( $product)){
foreach( $product as $p){
$html.=do_shortcode('[add_to_cart id="'.$p.'"]');
}
}elseif(!empty($product) ){
$html.=do_shortcode('[add_to_cart id="'.$product.'"]');
}
$html.='<style>.courseitem p.product.woocommerce.add_to_cart_inline {
border: none !important;
}</style>';
return $html;
}