Pixma mx 475. Worst buy ever! No wifi connection.

I´ve just bought a pixma mx 475 and it´s imposible to configure the wifi.
I don´t know why but it eventually appears in my network and i can use it.
But everytime i switch it off it disappears from the network and cant use it again.
And the i have to wait because i don´t know what to do to bring it back online.
When i print the lan settings, the printer is "connected", the networks ssid is printed, but there i no any ip assigned.
I don´t know what to do.