We need to install this plugin on our WordPress: https://wordpress.org/plugins/simple-image-sizes/
After installation active the plugin and go to the settings:
Click add a new size of thumbnail:
Click Validate and then save changes.
Go to Listivo Panel > Design > Listivo Ad Card and set it here.
Save changes and go back to the plugin settings and scroll to the bottom and hit button:
When the plugin it’s finished working you have all images on your page with the new size.