OSMC and VU+ addon : "connexion lost"


with my new RPi2, i downloaded the PVR “vu+ add-on” to stream my dreambox 800SE channels. I configured the port, user ID and password.
Then i have the message on the bottom right corner : “connexion lost” every few seconds.

i don’t understand because the password is good !??
i tried to connect with these id/passwd through FileZilla, a web page or with another software, the connection is ok !

is this a problem of compatibility between OSMC and VU+ ?