Directory errors


I have several errors with a directory install as follows;

1) Ratings are not working – I am able to select a rating from the dropdown menu but it has no effect.

2) With reading settings as ‘Front page displays latest posts’, the front page displays the categories, however, upon clicking the following error occurs;

Catchable fatal error: Object of class WP_Error could not be converted to string in /home/radlett/public_html/email/wp-content/plugins/directory/core/template-tags.php on line 149

3) when trying to view the listings page on a mobile I get the following;

Fatal error: Call to undefined function get_the_post_thumbnail() in/home/radlett/public_html/email/wp-content/plugins/directory/core/core.phpon line 904

Please advise.