second fix.php

<?php
// If Woo thinks payment is not required (total = 0), recalculate and force needs_payment = true.
add_filter( 'woocommerce_order_needs_payment', function( $needs_payment, $order ) {
    if ( $needs_payment || ! $order instanceof WC_Order ) {
        return $needs_payment;
    }
    if ( 0 === count( $order->get_items( 'line_item' ) ) ) {
        return $needs_payment;
    }

    // Recalculate totals from line items + shipping + fees + tax.
    $item_total     = array_sum( array_map( static fn( $i ) => (float) $i->get_total(), $order->get_items( 'line_item' ) ) );
    $fee_total      = array_sum( array_map( static fn( $f ) => (float) $f->get_total(), $order->get_fees() ) );
    $shipping_total = array_sum( array_map( static fn( $s ) => (float) $s->get_total(), $order->get_shipping_methods() ) );
    $shipping_tax   = array_sum( array_map( static fn( $s ) => (float) $s->get_total_tax(), $order->get_shipping_methods() ) );
    $tax_total      = (float) $order->get_total_tax();

    $calc_total = $item_total + $fee_total + $shipping_total + $tax_total;

    if ( $calc_total > 0 ) {
        // Force correct totals on the order object before payment is processed.
        $order->set_shipping_total( $shipping_total );
        $order->set_shipping_tax( $shipping_tax );
        $order->set_total( $calc_total );
        $order->update_meta_data( '_order_total', $calc_total );
        return true; // Force payment instead of allowing zero-total checkout
    }

    return $needs_payment;
}, 5, 2 );