This is more of a conflict with your theme rather than a bug in WPAdverts, resolving this requires some PHP/WordPress knowledge
1) Go to the wp-admin / Classifieds / Options / Core / Types panel, edit the Advert Categories taxonomy, go to the Rendering tab, and in the “Renderer Type” select “None”.
This should at least allow you to have the Advert Categories archive pages generated without any error.
2) create a category template as shown on the video here https://www.youtube.com/watch?v=GBW5pzI42nQ until 1:04. The important thing is that you name the template taxonomy-template.
3) the most difficult part that does not have exact instructions (as each theme is different) is to create a taxonomy-advert_category.php template file in your theme folder, copy to it content from archive.php or taxonomy.php file, and replace the code generating content with something like
<?php echo do_shortcode('[adverts_block template_name="taxonomy-template"]'); ?>
