access to internet problem

I have a router of NETGEAR Nighthawk R8000 after updating it to firmware Version 1.0.4.4, i started to face a problem with the computers and phones that use android OS , which is all these sets connect normally to wifi provided by my router but with no access to internet. I did a factory reset for my router but the problem presist. I also downgraded the router to the previous firmware, but to no avail, the problem continues.Would kindly help me to solve this problem.
All the best