In the end if someone has the same problem it was caused by a title with "à" character inside.
"[ERR] Error retrieving children folder
System.IO.FileNotFoundException: Can't find item path.
File name: '/Film/2016/The Belko Experiment - Chi sopravviver� (2016).1080p.mp4'"
After fixing the name everything started to work again even pointing directly "Film"
"[ERR] Error retrieving children folder
System.IO.FileNotFoundException: Can't find item path.
File name: '/Film/2016/The Belko Experiment - Chi sopravviver� (2016).1080p.mp4'"
After fixing the name everything started to work again even pointing directly "Film"