Reset the Wi-Fi and reconnect as is shown in a few videos below.
Wi-Fi reset 4100 vodeo
Wi-Fi connect video 4130
For Wi-Fi direct setupclick here. This is useful if there is no modem or you do not want to give someone access to your modem but you want to let them print something.
Simple push button or WPS setup is described on page 22 of User Manual
It could also be that your printer is going to sleep and when it wakes up it gets a different IP address. This can happen on flex systems. A quick fix is to disable sleep.
Let me know if you have a flex system (Wi-Fi boosters or repeaters) as the setup is much more complicated.