Why Lenovo Note4 mobile upgraded Android 6.0 often showing 'WiFi conection Failure'

[AC Question]

I have BSNL BB and using WiFi in 4-5 Laptops/Mobiles/Ipads at home. Recently after my Lenovo Note4 mobile is upgraded to Marshmellow, often "WiFi Connection Failure" happens. To test, I approached my neighbour running an office to access his WiFi network with the same mobile and I am able to get his WIFi and it is functioning well. If I access my WiFi again, I get WIFi Connection Failure message. After sometime it starts functioing. However, I don't know when I will get WiFi and when it will fail. Pretty unpredictable.
This BSNL WIFI connection problem is not happening in other mobiles or IPad or Laptops in my home. It is happening only in my Lenovo mobile.
Pl give a solution to this peculiar problem? My email id is (email address removed by moderator)

 

[dpham00]

Mod note, please do not post your email address on this public forum

 

[Rukbat]

Make sure that your BSNL router wireless page is set to WPA-PSK and AES.

 

[B. Diddy]

Welcome to Android Central! Also, try rebooting your home router by unplugging its power for 10 seconds, then plugging it back in again.