I can confirm this issue. Can you help me to resolve it?

In the file mc_file_api.php , line 97 ( if ( !file_exists( $t_upload_path ) || !is_dir( $t_upload_path ) || !is_writable( $t_upload_path ) || !is_readable( $t_upload_path ) ) { )

replace $t_upload_path by $t_file_path

That worked for me, hope it will for you ;p

It also worked for me, thank you! :)