Internet Connectivity issues?

I am not sure how many of my issues are related or if they are separate issues. We have three ASUS laptops/netbooks that somehow no longer connect to the internet. We have done diagnostics, the signal is strong, and yet they cannot connect. I think this has happened since the latest Windows update. 2 of the laptops are running Windows 8, and one is running Windows 7. I also have a smart tv that shows it has a strong signal, yet cannot connect to the internet.

I have and Apple Airport Extreme router, and an Airport Express that extends the network. All of our Apple products, such as iphones and ipads, have had no problems connecting to the internet. Some of the other computers in the house have not had a problem connecting. One of those is a Toshiba laptop running Windows 7 and has the latest Windows updates installed, yet not having this problem.

I am currently running two of the ASUS laptops connected through ethernet cables, but that is only temporary.

Thanks!