Nightawk M1: strange, lost connexion

Dear all,

I bought a new Nightawk M1.

Set-up OK : M1 used as router with WiFi off and connected to switch with cable then to a Wifi router. I set also ethernet sleeping: never.
Both from my laptop trought Ethernet cable and Wifi, i can go on Internet with M1. That's look fine.
I go away, laptop not stopped and come back 1 hours ago.
When i come back, i lost my Internet connection. I didn't do anything.
I check my laptop ethernet card and my IP changed ! strange. I force to be on a IP accepted by M1 router. And i can connect only to M1 router home page and can't go to Internet even if it is "connected" (see attached screenshot), on M1 dashboard webpage status
I reboot with M1 webpage , the Nightawk.
Same, i can't get Internet.
Then i reboot M1 with button on it and then i get again Internet.
Is there a set-up which M1 can lost connexion?
Any suggestion?
It is very strange. I reproduced all times this issue when wanted to use M1, go away and come back on laptop.
Thanks,
Tom