Help with category loop

you have missed to add $my_query-> to the_post();

i.e. change the start of the loop to:

<?php if ($my_query->have_posts()) : while ($my_query->have_posts()) : $my_query->the_post(); ?>

and replace

wp_reset_query();

with

wp_reset_postdata();

Thank you very much, that worked great, except I now my pagination has disappeared.

Any suggestions?

<?php 

          $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
          $my_query = new WP_Query(array('category__in' => array(4), 'posts_per_page' => 2,'paged'=>$paged)); ?>
          <?php if ($my_query->have_posts()) : while ($my_query->have_posts()) : $my_query->the_post(); ?>

                    <?php $currentid = get_the_id(); ?>

                    <div class="project-box grid-box grid-block mod-box width100">
                            <div class="project-img">
                                <?php if (get_the_post_thumbnail($currentid) != "") { ?>
                                   <a href="<?php the_permalink(); ?>" ><?php echo get_the_post_thumbnail($currentid,array(300,600)); ?></a>
                                <?php } else { ?>
                                    <a href="<?php the_permalink(); ?>" ><img src='<?php bloginfo('template_url') ?>/images/default.png' alt='Killen Civlil Engineering'/></a>
                                <?php } ?>
                            </div> 

                            <div class="project-info">
                                <h2><a href="<?php the_permalink(); ?>"><?php echo get_the_title($currentid); ?></a></h2>
                                <p><?php echo get_the_excerpt(); ?></p>
                                 <a href="<?php the_permalink(); ?>" class="info">More  ?</a>
                            </div>
                      </div> 

                <?php endwhile; ?>
              <div class="project-pagination">

                  <div class="pagination page-btn"><?php next_posts_link( '? Prev' ); ?></div>
                    <div class="pagination page-btn-1"><?php previous_posts_link( 'Next ?' ); ?></div>

              </div>  

            <?php
            endif;
            wp_reset_postdata();
?>

pagination:

<div class="pagination page-btn"><?php next_posts_link( '? Prev', $my_query->max_num_pages  ); ?></div>
                    <div class="pagination page-btn-1"><?php previous_posts_link( 'Next ?', $my_query->max_num_pages ); ?></div>

https://wordpress.stackexchange.com/questions/20424/wp-query-and-next-posts-link

That worked great thanks!! ??