We monitor the status of your router using a heartbeat signal that is sent by your router every hour. If we don’t detect a life signal we send you an email alert.
The email address on which you receive the alert can be modified in the control center under Tools-and-Settings > Your Profile. Secondary operators can have their own alert emails sent to the email address they set in the same menu.
If you receive an alert or see the router status as down, but the hotspot is working that means our servers cannot see your router. The life signal traffic can be blocked by a firewall in your network, especially by an SPI firewall. Turning it off can resolve the problem. 
You can turn off various system notifications, see: http://help.hotspotsystem.com/faq/where-can-i-turn-off-router-status-notifications
I receive several time a year this sort of message! Is there anything to do to avoid them?
-“ROUTER STATUS: DOWN
Last life signal sent: 2016-10-19 20:45:06 (GMT+01:00) Central European Time [2016-10-19 18:45:06 GMT]
Location: Villa La Palmeraie
MAC Address: c8-b3-73-26-95-cf”
-“ROUTER STATUS: UP
Last life signal sent: 2016-10-19 22:45:07 (GMT+01:00) Central European Time (2016-10-19 20:45:07 GMT)
Location: Villa La Palmeraie
MAC Address: c8-b3-73-26-95-cf”
No disclaim from users.
Thanks a lot. Patrice
You can turn Router Alert off in Control Center, under Settings.