There are 3 typos (or programming errors?) in the
plugin.php file. One of the post options is called
'postcards_enabled', but in 3 places in that file the author entered it as
'postcards_enable' (without the "
d" at the end). This causes the per-page enable/disable override feature to not work. (Specifically, the "enable" option to override a global disable.)
EASY FIX: Use the plugin editor feature on your WP Dashboard. If you text search through
plugin.php for the string
postcards_enable' (with the trailing single quote!) and add the letter "d" making it read
postcards_enabled' (note the "d" at the end of the word!) it will work.
WARNING: This "fix" will go away when this plugin is updated. Hopefully the author will make the fix himself. (Hint! Hint!) If not, admins will have to reapply this fix themselves.