MyRewards compatibility

Thank you for investigation.

Can you try percentage discount coupon with “Individual use only” and “Exclude sale items” both set to ON? We get this discount auto generated with Omnisend, that’s how we discovered combination of ADP ruled product + coupon + loyalty points do not stack in cart, and loyalty points are removed. I also turned off all plugins in dev environment, and get same result.

Here is a snippet from MyRewards to apply loyalty points with any coupons (it actually works, but not in combo described above). Maybe you can take a look and find a conflict or lack of logic?

/**
 * Stack *loyalty points* (MyRewards) with ANY coupon, even if that other coupon is "individual use".
 */

/** Detector: MyRewards points coupon? (by code prefix "mrwrds") */
if ( ! function_exists( 'km_is_loyalty_points_coupon' ) ) {
    function km_is_loyalty_points_coupon( $coupon ): bool {
        if ( $coupon instanceof WC_Coupon ) {
            $code = (string) $coupon->get_code();
        } else {
            $code = (string) $coupon; // coupon code string
        }
        return (bool) preg_match( '/^wr_points_on_cart/i', $code );
    }
}

/**
 * Allow applying a coupon even when an individual-use coupon is present,
 * IF either one is the loyalty points coupon.
 *
 * Signature: ($allow, WC_Coupon $coupon, WC_Coupon $individual_use_coupon, array $applied_coupons)
 */
add_filter( 'woocommerce_apply_with_individual_use_coupon', function( $allow, $coupon, $individual_use_coupon = null, $applied_coupons = array() ) {
    if ( $coupon instanceof WC_Coupon && km_is_loyalty_points_coupon( $coupon ) ) {
        return true; // always allow adding loyalty alongside individual-use
    }
    if ( $individual_use_coupon instanceof WC_Coupon && km_is_loyalty_points_coupon( $individual_use_coupon ) ) {
        return true; // allow adding any coupon if the existing individual-use is actually loyalty
    }
    return $allow;
}, 10, 4 );

/**
 * When an individual-use coupon is applied, Woo would remove other coupons.
 * Keep removing others as usual, EXCEPT never remove the loyalty points coupon.
 *
 * Signature: ($to_remove, WC_Coupon $coupon, array $applied_coupons)
 */
add_filter( 'woocommerce_apply_individual_use_coupon', function( $to_remove, $coupon, $applied_coupons = array() ) {
    // If we are applying the loyalty coupon, never remove anything.
    if ( $coupon instanceof WC_Coupon && km_is_loyalty_points_coupon( $coupon ) ) {
        return array();
    }

    // Otherwise (applying some other coupon, possibly individual-use),
    // do not remove the loyalty coupon from the cart.
    $filtered = array();
    foreach ( (array) $to_remove as $code ) {
        if ( ! km_is_loyalty_points_coupon( $code ) ) {
            $filtered[] = $code;
        }
    }
    return $filtered;
}, 10, 3 );

/**
 * Safety: ensure loyalty coupons are never treated as "individual use".
 * (If MyRewards ever marks them so, override at runtime.)
 *
 * Signature: ($is_individual_use, WC_Coupon $coupon)
 */
add_filter( 'woocommerce_coupon_get_individual_use', function( $is_individual, $coupon ) {
    if ( $coupon instanceof WC_Coupon && km_is_loyalty_points_coupon( $coupon ) ) {
        return false;
    }
    return $is_individual;
}, 10, 2 );