Thanks Allan for you reply. I did already the modification of the jpg or whatever image files, but this is too long for an ads site where people are continuosly uploading images.

If you could let me know which php files you have modified and how, i'll really appreciate. This will work automatically for the future and for any update i'll eventually remodify the php files.

Anyway it sound strange that it is not possible to config the adsmanager to have thumbnails automatically.

Please let me know.

Continuously, sounds like you have a heavy load, at your own risk, drop me a mail to
JoomlaTim at yahoo.ca, this is not the place to post such hacks.

I was thinking that ADSmanager convert AUTOMATICALLY the images in thumbnails. We are the only two guys having problem with it or it is a feature of the extensions?

I made an override of the file default_list.php (components/com_adsmanager/views/list/tmpl) and changed

<?php
if (isset($content->images[0])) {
echo "<a href='".$linkTarget."'><img class='ad-image' name='ad-image".$content->id."' src='".$this->baseurl."images/com_adsmanager/ads/".$content->images[0]->thumbnail."' alt=\"".htmlspecialchars($content->ad_headline)."\" /></a>";
} else if ($this->conf->nb_images > 0) {
echo "<a href='".$linkTarget."'><img class='ad-image' src='".ADSMANAGER_NOPIC_IMG."' alt='nopic' /></a>";
}
?>

in

<?php
if (isset($content->images[0])) {
echo "<a href='".$linkTarget."'><img class='ad-image' name='ad-image".$content->id."' src='".$this->baseurl."images/com_adsmanager/contents/".$content->images[0]->thumbnail."' alt=\"".htmlspecialchars($content->ad_headline)."\" /></a>";
} else if ($this->conf->nb_images > 0) {
echo "<a href='".$linkTarget."'><img class='ad-image' src='".ADSMANAGER_NOPIC_IMG."' alt='nopic' /></a>";
}
?>

(short: change "ads" in "contents")

That worked for me as a work around. At least now a picture is shown in the list view.
I need to add that I had this problem, of not showing thumbnails in list view, since the beginning of december 2015. It must have been bc of installing the last update end of november/early december that caused this problem.