the problem is in the script
/wp-content/plugins/fs-real-estate-plugin/includes/admin_listings.php
there is the variable $CurrentURL around line 22 used for generating links.
$CurrentURL = ‘https://’.$_SERVER[“SERVER_NAME”].$_SERVER[“REQUEST_URI”];
so the sessions don’t work if you login on your domain with ‘www.domain.tld’ and click on the ‘edit’ link that goes to ‘domain.tld’. So you get the wp login-screen. Behaviour depends on server settings.
I just quickly changed this to
$CurrentURL = ‘https://www.’.$_SERVER[“SERVER_NAME”].$_SERVER[“REQUEST_URI”];