@RedaEL 

I think you're having the same issue as the Iranian user whose also posted so here's the reply I gave him,

If it's  a wifi connected device there is an issue with hidden networks, so if the SSID is turned off on the router the phone/tab/chromebook may struggle to connect or remain connected, this is especially bad on the 5ghz band,

Solution is when setting up the device to connect to the router to select advanced settings on the device wishing to connect after entering username encyption and password settings, this drops down to be able to select Hidden Network then save, that's supposed to sort it but doesn't always,

Short version

If you have the router set to not broadcast it's wifi ID's there is the possibility of connection problems, it's something to do with Google updating their security settings and possible Apple has done the same thing, hth.

@RedaEL Hi All,

Sorry to be late to reply, that because i try to apply all your advices in my router settings.

Sadly i still have to same issue in all my devices (iMac, android phone).

Thing i do :

-reset the router with factory setting.

-change channels from auto to 2, 6 and 11.

-run the router with the last update "3.0.0 Build 180118 Rel.05999"

if is there any other solution can do ? Thank you