can not synchronize a new magazine

What happened with this plugin?
I can not synchronize a new magazine with Issuu! This I always done within the plugin – Issuu PDF Sync. The older publications files are synchronized.
Now , when I try to do it, the inscription appears: An error occured during synchronisation .
My web http://www.mamairvaikas.lt/tvs/lt/leidiniai/naujas-zurnalas. I m using worpress 3.6

https://wordpress.org/plugins/issuu-pdf-sync/