Loss of connection on long prints

In long prints of more than 20 hours or in pauses of more than 3 or 4 hours, when I try to access mainsail I get a connection error, I have been experiencing the problem for some time, I have tried to increase the idle time out and to install sonar to keep the connection active, but nothing solves the problem. I have also noticed that when I get this error the raspberry pi does not appear in the list of devices connected to the router.