If you get an error message like this

“Fatal error: Cannot redeclare run_treepress() (previously declared in …/public_html/wp-content/plugins/treepress/treepress.php:125) in …/public_html/wp-content/plugins/treepress-premium/treepress.php on line 125”

when installling the Premium version of the plugin, please check and disable the Free verson.