Hello again.
I found the solution.

STEP 1: I added the code below inside
<span class=”image-overlay overlay-type-image” style=”left: 1.99219px; top: 0px; overflow: hidden; display: block; height: 100%; width: 98%; border-radius:5px;”><span class=”image-overlay-inside”></span></span>’

Example:
echo ‘<div class=”avia-image-container avia-align-center “><div class=”avia-image-container-inner”><a class=”lightbox avia_image” ‘
. ‘ href=”myPhotoURL” target=”_blank”><img class=”avia_image ” title=”” ‘
. ‘ src=”myPhotoURL” ‘
. ‘ alt=”myALTtext” />’
. ‘ <span class=”image-overlay overlay-type-image” style=”left: 1.99219px; top: 0px; overflow: hidden; display: block; height: 100%; width: 98%; border-radius:5px;”><span class=”image-overlay-inside”></span></span>’
. ‘</div>’
.'</div>’;

STEP 2:
After ajax code is finished, you must run this code to reload lightbox:

//activates the lightbox
if($.fn.avia_activate_lightbox){
$(‘body’).avia_activate_lightbox();
}

Thank you!!!

It works.

WeI used array(‘avia-scs’, ‘avia-merged-styles’) because we want to work also if the switch “compress for performance” is enabled.